glapi: generate static offsets from the list of GL functions automatically

Since glapi is part of libgallium.so, the offsets don't have to be immutable
anymore, but they still have to be fixed values within a build because both
gl_XML.py and genCommon.py use them and they should match AFAIK.

Reviewed-by: Adam Jackson <ajax@redhat.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/33634>

src/mapi/glapi/gen/gl_XML.py

@@ -661,9 +661,8 @@ class gl_function( gl_item ):
 
             if name in static_data.offsets:
                 self.offset = static_data.offsets[name]
-            else:
-                if self.exec_flavor != "skip":
-                    raise RuntimeError("Entry-point %s is missing offset in static_data.py. Add one at the bottom of the list." % (name))
+            elif self.exec_flavor != "skip":
+                raise RuntimeError("Entry-point %s is missing in static_data.py. Add one into all_functions." % (name))
 
         if not self.name:
             self.name = true_name