Comment 2 for bug 1794542

Reviewed: https://review.openstack.org/605458
Committed: https://git.openstack.org/cgit/openstack/stx-root/commit/?id=91f3b6f899776cbb9f5bc85a7c1dfe96dc261927
Submitter: Zuul
Branch: master

commit 91f3b6f899776cbb9f5bc85a7c1dfe96dc261927
Author: Scott Little <email address hidden>
Date: Wed Sep 26 11:06:40 2018 -0400

    build-pkg pkg-name of std pkg causes rt build failure

    Brief Description
    -----------------
    Designer issues 'build-pkg pkg-name' where pkg-name is only valid for
    std builds.

    Expected result is that only 'std' build is executed on the named
    package.
    What is observed is that aftes a successful std build, an 'rt' build is
    executed with an invalid package list causing a failure.

    The package is built correctly, but command returns 1.
    This breaks scripts that test build-pkgs return code.

    Problem
    -------
    find_targets returned $EMPTY_LIST rather than $EMPTY_TARGETS as expected.

    Solution
    --------
    find_targets must return $EMPTY_TARGETS when no targets are found for
    the build type.

    Closes-Bug: 1794542
    Change-Id: I3d21bb793b1fc9637b16a08fdfcd2fd998742bfb
    Signed-off-by: Scott Little <email address hidden>