GLSL/SPV: no location on atomic_uint; Fix #1339.

Test/spv.noBuiltInLoc.vert

@@ -10,6 +10,8 @@ uniform vec4 uv1;
 uniform float uv2;
 uniform vec3 uv3;
 
+layout(binding = 0) uniform atomic_uint a_uint;
+
 void main()
 {
     bar = foo;