build: Skip vulkan parts in generated GLSL

Make the #include parsing script able to skip a predefined list of terms
with #ifdef

Put "VULKAN" in that list to skip the vulkan parts.

gsk/gpu/shaders/common.glsl

@@ -7,9 +7,13 @@ void            main_clip_rounded               (void);
 
 #include "enums.glsl"
 
+/* Needs to be exactly like this and not use #else
+ * because our include script is too dumb
+ */
 #ifdef VULKAN
 #include "common-vulkan.glsl"
-#else
+#endif /* VULKAN */
+#ifndef VULKAN
 #include "common-gl.glsl"
 #endif
 

gsk/gpu/shaders/process-glsl-includes.py

@@ -6,17 +6,37 @@ import os
 
 loaded_files = []
 
+check_defines = [ 'VULKAN' ]
+
 def load (path):
     if (path in loaded_files):
         return
 
     loaded_files.append (path)
+    skipping = ''
 
     with open(path) as f:
         lines = f.readlines()
         for line in lines:
+            if skipping:
+                match = re.search (r"^#endif /\* (.*) \*/$", line)
+                if match and match.group(1) == skipping:
+                    skipping = ''
+                continue
+
+            match = re.search (r"^#define (.*)$", line)
+            if match and match.group(1) in check_defines:
+                check_defines.remove (match.group(1))
+                print (line, end="")
+                continue
+
+            match = re.search (r"^#ifdef (.*)$", line)
+            if match and match.group(1) in check_defines:
+                skipping = match.group(1)
+                continue
+
             match = re.search (r"^#include \"(.*)\"$", line)
-            if (match):
+            if match:
                 load (os.path.join (os.path.dirname(path), match.group(1)))
             else:
                 print (line, end="")