Make installed-tests executable.
Meson tries to execute them directly, causing autopkgtests to fail with
FAIL: gtk-4.0/tools/settings.test (Child process exited with code 126)
FAIL: gtk-4.0/tools/simplify.test (Child process exited with code 126)Meson tries to execute them directly, causing autopkgtests to fail with
FAIL: gtk-4.0/tools/settings.test (Child process exited with code 126)
FAIL: gtk-4.0/tools/simplify.test (Child process exited with code 126)