VAPI build fails on older versions of valac in 10.04 and 10.10

[dobey]

The nightlies are currently failing on Lucid and Maverick with the following error:

/usr/bin/valac --pkg gobject-2.0 --pkg glib-2.0 -C libsyncdaemon-1.0.vapi test-libsyncdaemon-vapi.vala
test-libsyncdaemon-vapi.vala:20.7-20.16: error: The namespace name `Syncdaemon' could not be found
using Syncdaemon;
      ^^^^^^^^^^
Compilation failed: 1 error(s), 0 warning(s)
make[3]: *** [test_libsyncdaemon_vapi_vala.stamp] Error 1

This is because the older versions of valac on those Ubuntu versions do not support passing the .vapi in as a source file. Instead, to support building here, we must depend on the .vapi being built explicitly, and pass --vapidir=$(builddir) and --pkg libsyncdaemon-1.0 to the build of test-libsyncdaemon-vapi to ensure it builds.

[dobey (dobey)]

Rather, the error was somewhat misleading. The real problem was that the gir file has not been built properly, and so the build failed on older versions, where g-ir-scanner did not support the --identifier-prefix option.