Wait a minute! It's working! But the only way to work is with the LD_LIBRARY_PATH set. I installed mesa and set the LD_LIBRARY_PATH from my command line, an icecat run from the command line works, the one run from the desktop environment doesn't.
So... guix is not setting the LD_LIBRARY_PATH correctly for Mesa and that's why IceCat is unable to find it?
