glsl: Allow invariant qualifer in block members in desktop OpenGL.

Feedback from Khronos is that 'invariant' should be allowed on block
members for desktop OpenGL. Fix piglit regression added by fe1e89a0:
invariant-qualifier-in-out-block-01.vert

v2:
- Allow it for in/out blocks in OpenGL ES too, so when OES_shader_io_blocks
is supported we don't need to do any change (Timothy)

Bugzilla: https://bugs.freedesktop.org/show_bug.cgi?id=89330
Signed-off-by: Samuel Iglesias Gonsálvez <siglesias@igalia.com>
Reviewed-by: Timothy Arceri <timothy.arceri@collabora.com>

src/compiler/glsl/glsl_parser_extras.cpp

@@ -944,27 +944,11 @@ _mesa_ast_process_interface_block(YYLTYPE *locp,
                           "the interface block");
       }
 
-      /* From GLSL ES 3.0, chapter 4.3.7 "Interface Blocks":
-       *
-       * "GLSL ES 3.0 does not support interface blocks for shader inputs or
-       * outputs."
-       *
-       * And from GLSL ES 3.0, chapter 4.6.1 "The invariant qualifier":.
-       *
-       * "Only variables output from a shader can be candidates for
-       * invariance."
-       *
-       * From GLSL 4.40 and GLSL 1.50, section "Interface Blocks":
-       *
-       * "If optional qualifiers are used, they can include interpolation
-       * qualifiers, auxiliary storage qualifiers, and storage qualifiers
-       * and they must declare an input, output, or uniform member
-       * consistent with the interface qualifier of the block"
-       */
-      if (qualifier.flags.q.invariant)
+      if (!(q.flags.q.in || q.flags.q.out) && qualifier.flags.q.invariant)
          _mesa_glsl_error(locp, state,
-                          "invariant qualifiers cannot be used "
-                          "with interface blocks members");
+                          "invariant qualifiers can be used only "
+                          "in interface block members for shader "
+                          "inputs or outputs");
    }
 }