[cogl] build: fix building test-gles2-context

[Robert Bragg <rbragg src gnome org>]

commit e5b24540a6a18d089c56ca186754b82e7d280d5c
Author: Robert Bragg <robert linux intel com>
Date:   Thu Jun 6 21:59:51 2013 +0100

    build: fix building test-gles2-context
    
    This makes sure we build the conform tests with -I$(top_builddir)/cogl
    to be able to find cogl-gl-header.h

 tests/conform/Makefile.am |    1 +
 1 files changed, 1 insertions(+), 0 deletions(-)
---
diff --git a/tests/conform/Makefile.am b/tests/conform/Makefile.am
index e9ebe14..8cf3281 100644
--- a/tests/conform/Makefile.am
+++ b/tests/conform/Makefile.am
@@ -120,6 +120,7 @@ BUILT_SOURCES = wrappers
 
 AM_CPPFLAGS = \
        -I$(top_srcdir) \
+       -I$(top_builddir)/cogl \
        -I$(top_srcdir)/test-fixtures
 
 if !USE_GLIB