mesa: Apply visibility flags to src/Makefile.am targets

We were building libglsl_util.la without our visibility flags and
leaking hash_table_* symbols.

Signed-off-by: Kristian Høgsberg <kristian.h.kristensen@intel.com>
Reviewed-by: Matt Turner <mattst88@gmail.com>
diff --git a/src/Makefile.am b/src/Makefile.am
index 8edf333..874a333 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -55,6 +55,9 @@
 
 EXTRA_DIST = egl/docs getopt hgl SConscript
 
+AM_CFLAGS = $(VISIBILITY_CFLAGS)
+AM_CXXFLAGS = $(VISIBILITY_CXXFLAGS)
+
 AM_CPPFLAGS = \
 	-I$(top_srcdir)/include/ \
 	-I$(top_srcdir)/src/mapi/ \