assert-msg-test.py: Look for assert-msg-test relative to this script
When run as an installed-test, assert-msg-test generally won't be in the PATH, but it will be in the same directory as the installed copy of this script, so we can find it that way.
This fixes an installed-tests failure in Debian's autopkgtest environment.
gobject/tests/performance: Use the other installed-tests template
These are not GTest tests, and don't output TAP.
gobject/tests/performance: Only run a quick version as installed-tests
ginsttest-runner defaults to timing out each test after 5 minutes, but gobject/tests/performance/performance.c defaults to running each of 18 tests for 15 seconds. The result is close enough to 5 minutes that the setup overhead is enough to make it time out.
We're only running these tests to prove that they still work, not to get meaningful performance numbers, so cut them down to 1 second per test-case (the result of which is that performance.c takes about a minute).