Make glsl-fface-invariant accept either compile or link errors

The old version of the test assumed the compiler would generate a link error, but it's equally valid to generate a compile-time error.

There isn't a great way to do this in shader_runner (which assumes shaders compile), or glslparsertest (which only works on a single shader, and GLSL ES requires both a VS and FS in order to link).

So, we port the test to C. It's simpler than adding infrastructure.