Test case for GL pkgconfig dependency

Test that the GL pkgconfig dependency is actually a pkgconfig dependency

test cases/common/174 dependency factory/meson.build

@@ -0,0 +1,6 @@
+project('dependency factory')
+
+dep = dependency('gl', method: 'pkg-config', required: false)
+if dep.found() and dep.type_name() == 'pkgconfig'
+  dep.get_pkgconfig_variable('prefix')
+endif