On today's Rawhide, steam doesn't work anymore. I got an error about the GLX context not using direct rendering. Further investigation shows that the version of libgcc_s in Steam is incompatible with Fedora Rawhide's version of GCC, and thus Steam cannot load graphic drivers compiles by Fedora:

libGL error: dlopen /usr/lib/dri/radeonsi_dri.so failed (/home/elad/.local/share/Steam/ubuntu12_32/steam-runtime/i386/lib/i386-linux-gnu/libgcc_s.so.1: version `GCC_4.7.0' not found (required by /usr/lib/dri/radeonsi_dri.so))
libGL error: unable to load driver: radeonsi_dri.so