* ci: add Linux GCC/Clang workflow
Add a Linux job that builds with GCC and Clang using Ninja and runs tests
* ci: install OpenGL headers on Linux
Fix raylib configure by installing libgl-dev in the Linux GCC/Clang job
* ci: enable SSE4.1 for Linux builds
Pass -msse4.1 to GCC/Clang in the Linux workflow to satisfy runtime intrinsics