Mesa provides pkg-config files for egl, glesv2, gl, as well as wayland-egl. It would be nice if automake/autoconf could preferentially use this, only falling back to platform-specific checks where these pkg-config files are not provided.

This is already used in Weston, other parts of GNOME, etc. It would be much nicer to use these instead of having to manually set CFLAGS/LDFLAGS just for these libraries.

I found this because I have $PKG_CONFIG_PATH and $LD_LIBRARY_PATH set to include my own custom Mesa build, where they have conflicting settings such that linking fails if -lGL points to the system libGL. So far this is the only component I've found not making use of Mesa's pkg-config files. (Currently only Mesa ships these, however I know of at least one proprietary stack which is beginning to provide them.)

Funnily enough, this caused all of OpenGL/GLES to not be found, but EGL to be marked as found: in that case, it goes on to compile gst-gl anyway, and blows up pretty spectacularly as GLint/etc are never defined.