build: don't include deps/glib headers if glib enabled

If we're using the system glib library then we need to make sure not to
include headers under deps/glib otherwise we end up with with
incompatible typedefs that break the build.

Reviewed-by: Neil Roberts <neil@linux.intel.com>

(cherry picked from commit 5d5fc97b59951ec56a4193b7ee7909ebd3cfbb94)

examples/Makefile.am

@@ -1,8 +1,11 @@
 include $(top_srcdir)/build/autotools/Makefile.am.silent
 
 INCLUDES = \
-	-I$(top_srcdir) \
-	-I$(top_builddir)/deps/glib
+	-I$(top_srcdir)
+
+if !USE_GLIB
+INCLUDES += -I$(top_builddir)/deps/glib
+endif
 
 AM_CFLAGS = \
 	$(COGL_DEP_CFLAGS) \
@@ -17,9 +20,12 @@ endif
 
 common_ldadd = \
 	$(COGL_DEP_LIBS) \
-	$(top_builddir)/deps/glib/libglib.la \
 	$(top_builddir)/cogl/libcogl.la
 
+if !USE_GLIB
+common_ldadd += $(top_builddir)/deps/glib/libglib.la
+endif
+
 programs = cogl-info
 
 cogl_info_SOURCES = cogl-info.c