[gtk/wip/chergert/gdk-macos-gl-renderer: 3/6] glsl: tweak pre-processor to support Apple GLSL compiler

[Christian Hergert <chergert src gnome org>]

commit 50f8e1c734f526e5ba9f72a895a4eb01bdd4f4bf
Author: Christian Hergert <chergert redhat com>
Date:   Thu Oct 29 09:37:33 2020 -0700

    glsl: tweak pre-processor to support Apple GLSL compiler
    
    The Apple GLSL compiler cannot deal with empty pre-processor blocks such as
    
      #if GSK_GLES
      #elif GSK_LEGACY

 gsk/resources/glsl/preamble.fs.glsl | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)
---
diff --git a/gsk/resources/glsl/preamble.fs.glsl b/gsk/resources/glsl/preamble.fs.glsl
index 85b11c013e..c2cd1cdc29 100644
--- a/gsk/resources/glsl/preamble.fs.glsl
+++ b/gsk/resources/glsl/preamble.fs.glsl
@@ -5,10 +5,9 @@ uniform float u_alpha;// = 1.0;
 uniform vec4 u_viewport;
 uniform vec4[3] u_clip_rect;
 
-#if GSK_GLES
-#elif GSK_LEGACY
+#if defined(GSK_LEGACY)
 _OUT_ vec4 outputColor;
-#else
+#elif !defined(GSK_GLES)
 _OUT_ vec4 outputColor;
 #endif