XCB/GLX: we don't need GL Utilities, only GLX

configure.ac

@@ -3684,7 +3684,7 @@ AC_ARG_ENABLE(glx,
 ])
 AS_IF([test "${enable_glx}" != "no"], [
   PKG_CHECK_MODULES(XLIB_XCB, [x11-xcb])
-  PKG_CHECK_MODULES(GLU, [glu])
+  PKG_CHECK_MODULES(GL, [gl])
 
   VLC_ADD_PLUGIN([xcb_glx])
 ])

modules/video_output/Modules.am

@@ -48,9 +48,9 @@ libxcb_glx_plugin_la_SOURCES = \
 	xcb/glx.c \
 	xcb/events.c
 libxcb_glx_plugin_la_CFLAGS = $(AM_CFLAGS) \
-	$(XLIB_XCB_CFLAGS) $(GLU_CFLAGS)
+	$(XLIB_XCB_CFLAGS) $(GL_CFLAGS)
 libxcb_glx_plugin_la_LIBADD = $(AM_LIBADD) \
-	$(XLIB_XCB_LIBS) $(GLU_LIBS)
+	$(XLIB_XCB_LIBS) $(GL_LIBS)
 libxcb_glx_plugin_la_DEPENDENCIES =
 
 libxcb_window_plugin_la_SOURCES = xcb/window.c xcb/keys.c