The libGL.la and libGLU.la files installed by mesa explicitly add -L/usr/lib to the LDFLAGS of any package using them, thus forcing them to use the native libraries when crosscompiling. Another problem is that libGLU is written in C++ but used by many C only programs. It's best to add -lstdc++ to the dependencies list of libGLU. Reproducible: Always Steps to Reproduce:
Created attachment 189532 [details, diff] Remove -L/usr/lib from libGL.a
Created attachment 189534 [details, diff] Remove -L/usr/lib from libGLU.a and add -lstdc++
Okey applied for now, thanks for patches. Hopefully we will get rid of these two files soon.