Allow using system dependencies

[Jan Tojnar]

On NixOS, running the tests fails with the following:

> UpdateCTestConfiguration from :/build/lib2geom-1.0.0/build/DartConfiguration.tcl
> UpdateCTestConfiguration from :/build/lib2geom-1.0.0/build/DartConfiguration.tcl
> Test project /build/lib2geom-1.0.0/build
> Constructing a list of tests
> Done constructing a list of tests
> Updating test list for fixtures
> Added 0 tests to meet fixture requirements
> Checking test dependency graph...
> Checking test dependency graph end
> test 1
> Start 1: affine-test
>
> 1: Test command: /build/lib2geom-1.0.0/build/src/tests/affine-test
> 1: Test timeout computed to be: 10000000
> 1: /build/lib2geom-1.0.0/build/src/tests/affine-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 1/20 Test #1: affine-test ......................***Failed 0.00 sec
> test 2
> Start 2: angle-test
>
> 2: Test command: /build/lib2geom-1.0.0/build/src/tests/angle-test
> 2: Test timeout computed to be: 10000000
> 2: /build/lib2geom-1.0.0/build/src/tests/angle-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 2/20 Test #2: angle-test .......................***Failed 0.00 sec
> test 3
> Start 3: bezier-test
>
> 3: Test command: /build/lib2geom-1.0.0/build/src/tests/bezier-test
> 3: Test timeout computed to be: 10000000
> 3: /build/lib2geom-1.0.0/build/src/tests/bezier-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 3/20 Test #3: bezier-test ......................***Failed 0.00 sec
> test 4
> Start 4: choose-test
>
> 4: Test command: /build/lib2geom-1.0.0/build/src/tests/choose-test
> 4: Test timeout computed to be: 10000000
> 4: /build/lib2geom-1.0.0/build/src/tests/choose-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 4/20 Test #4: choose-test ......................***Failed 0.00 sec
> test 5
> Start 5: circle-test
>
> 5: Test command: /build/lib2geom-1.0.0/build/src/tests/circle-test
> 5: Test timeout computed to be: 10000000
> 5: /build/lib2geom-1.0.0/build/src/tests/circle-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 5/20 Test #5: circle-test ......................***Failed 0.00 sec
> test 6
> Start 6: convex-hull-test
>
> 6: Test command: /build/lib2geom-1.0.0/build/src/tests/convex-hull-test
> 6: Test timeout computed to be: 10000000
> 6: /build/lib2geom-1.0.0/build/src/tests/convex-hull-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 6/20 Test #6: convex-hull-test .................***Failed 0.00 sec
> test 7
> Start 7: coord-test
>
> 7: Test command: /build/lib2geom-1.0.0/build/src/tests/coord-test
> 7: Test timeout computed to be: 10000000
> 7: /build/lib2geom-1.0.0/build/src/tests/coord-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 7/20 Test #7: coord-test .......................***Failed 0.00 sec
> test 8
> Start 8: ellipse-test
>
> 8: Test command: /build/lib2geom-1.0.0/build/src/tests/ellipse-test
> 8: Test timeout computed to be: 10000000
> 8: /build/lib2geom-1.0.0/build/src/tests/ellipse-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 8/20 Test #8: ellipse-test .....................***Failed 0.00 sec
> test 9
> Start 9: elliptical-arc-test
>
> 9: Test command: /build/lib2geom-1.0.0/build/src/tests/elliptical-arc-test
> 9: Test timeout computed to be: 10000000
> 9: /build/lib2geom-1.0.0/build/src/tests/elliptical-arc-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 9/20 Test #9: elliptical-arc-test ..............***Failed 0.00 sec
> test 10
> Start 10: intersection-graph-test
>
> 10: Test command: /build/lib2geom-1.0.0/build/src/tests/intersection-graph-test
> 10: Test timeout computed to be: 10000000
> 10: /build/lib2geom-1.0.0/build/src/tests/intersection-graph-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 10/20 Test #10: intersection-graph-test ..........***Failed 0.00 sec
> test 11
> Start 11: line-test
>
> 11: Test command: /build/lib2geom-1.0.0/build/src/tests/line-test
> 11: Test timeout computed to be: 10000000
> 11: /build/lib2geom-1.0.0/build/src/tests/line-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 11/20 Test #11: line-test ........................***Failed 0.00 sec
> test 12
> Start 12: nl-vector-test
>
> 12: Test command: /build/lib2geom-1.0.0/build/src/tests/nl-vector-test
> 12: Test timeout computed to be: 10000000
> 12: /build/lib2geom-1.0.0/build/src/tests/nl-vector-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 12/20 Test #12: nl-vector-test ...................***Failed 0.00 sec
> test 13
> Start 13: path-test
>
> 13: Test command: /build/lib2geom-1.0.0/build/src/tests/path-test
> 13: Test timeout computed to be: 10000000
> 13: /build/lib2geom-1.0.0/build/src/tests/path-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 13/20 Test #13: path-test ........................***Failed 0.00 sec
> test 14
> Start 14: point-test
>
> 14: Test command: /build/lib2geom-1.0.0/build/src/tests/point-test
> 14: Test timeout computed to be: 10000000
> 14: /build/lib2geom-1.0.0/build/src/tests/point-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 14/20 Test #14: point-test .......................***Failed 0.00 sec
> test 15
> Start 15: polynomial-test
>
> 15: Test command: /build/lib2geom-1.0.0/build/src/tests/polynomial-test
> 15: Test timeout computed to be: 10000000
> 15: /build/lib2geom-1.0.0/build/src/tests/polynomial-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 15/20 Test #15: polynomial-test ..................***Failed 0.00 sec
> test 16
> Start 16: rect-test
>
> 16: Test command: /build/lib2geom-1.0.0/build/src/tests/rect-test
> 16: Test timeout computed to be: 10000000
> 16: /build/lib2geom-1.0.0/build/src/tests/rect-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 16/20 Test #16: rect-test ........................***Failed 0.00 sec
> test 17
> Start 17: sbasis-test
>
> 17: Test command: /build/lib2geom-1.0.0/build/src/tests/sbasis-test
> 17: Test timeout computed to be: 10000000
> 17: /build/lib2geom-1.0.0/build/src/tests/sbasis-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 17/20 Test #17: sbasis-test ......................***Failed 0.00 sec
> test 18
> Start 18: sbasis-text-test
>
> 18: Test command: /build/lib2geom-1.0.0/build/src/tests/sbasis-text-test
> 18: Test timeout computed to be: 10000000
> 18: /build/lib2geom-1.0.0/build/src/tests/sbasis-text-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 18/20 Test #18: sbasis-text-test .................***Failed 0.01 sec
> test 19
> Start 19: root-find-test
>
> 19: Test command: /build/lib2geom-1.0.0/build/src/tests/root-find-test
> 19: Test timeout computed to be: 10000000
> 19: /build/lib2geom-1.0.0/build/src/tests/root-find-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 19/20 Test #19: root-find-test ...................***Failed 0.00 sec
> test 20
> Start 20: implicitization-test
>
> 20: Test command: /build/lib2geom-1.0.0/build/src/tests/implicitization-test
> 20: Test timeout computed to be: 10000000
> 20: /build/lib2geom-1.0.0/build/src/tests/implicitization-test: error while loading shared libraries: libgtest.so: cannot open shared object file: No such file or directory
> 20/20 Test #20: implicitization-test .............***Failed 0.00 sec
>
> 0% tests passed, 20 tests failed out of 20
>
> Total Test time (real) = 0.04 sec
>
> The following tests FAILED:
> 1 - affine-test (Failed)
> 2 - angle-test (Failed)
> 3 - bezier-test (Failed)
> 4 - choose-test (Failed)
> 5 - circle-test (Failed)
> 6 - convex-hull-test (Failed)
> 7 - coord-test (Failed)
> 8 - ellipse-test (Failed)
> 9 - elliptical-arc-test (Failed)
> 10 - intersection-graph-test (Failed)
> 11 - line-test (Failed)
> 12 - nl-vector-test (Failed)
> 13 - path-test (Failed)
> 14 - point-test (Failed)
> 15 - polynomial-test (Failed)
> 16 - rect-test (Failed)
> 17 - sbasis-test (Failed)
> 18 - sbasis-text-test (Failed)
> 19 - root-find-test (Failed)
> 20 - implicitization-test (Failed)
> Errors while running CTest

Apparently, it tries to use vendored gtest instead of the system one and it fails.

[Patrick Storz (ede123)]

Closing in favor of https://gitlab.com/inkscape/lib2geom/issues/4