meson: fix glx-test race

This test should rely on dispatch.h being generated, but it doesn't.

Signed-off-by: Dylan Baker <dylanx.c.baker@intel.com>
Reviewed-by: Eric Anholt <eric@anholt.net>
diff --git a/src/glx/tests/meson.build b/src/glx/tests/meson.build
index d81b769..51b2843 100644
--- a/src/glx/tests/meson.build
+++ b/src/glx/tests/meson.build
@@ -35,7 +35,7 @@
 
   glx_test = executable(
     'glx-test',
-    [files_glx_test, glx_indirect_size_h],
+    [files_glx_test, glx_indirect_size_h, main_dispatch_h],
     link_with : [libglx, libglapi],
     include_directories : [
       include_directories('..', '../../../include/GL/internal'),