glsl/tests: Handle windows \r\n new lines

Currently the praser for s expressions assumes that newlines will be \n,
resulting in incorrect parsing on windows, where the newline is \r\n.
This patch just adds \r? to the regular expression used to parse the s
expressions, which fixes at 1 test on windows.

Reviewed-by: Eric Engestrom <eric.engestrom@intel.com>