glsl: include C11 compat header for static_assert()

Closes: mesa/mesa#1845
Fixes: b3e3af0e ("glsl: turn runtime asserts of compile-time value into compile-time asserts")
Signed-off-by: Eric Engestrom <eric.engestrom@intel.com>
47 jobs for !2248 with bug-1845 in 22 minutes and 54 seconds (queued for 4 seconds)
merge request