[base-gcc/sparc64] Fix graphics/graphene build

In file included from /usr/local/include/glib-2.0/glib/gtestutils.h:30,
from /usr/local/include/glib-2.0/glib.h:85,
from /usr/local/include/glib-2.0/gobject/gbinding.h:28,
from /usr/local/include/glib-2.0/glib-object.h:22,
from ../graphene-1.10.2/include/graphene-gobject.h:28,
from ../graphene-1.10.2/src/graphene-gobject.c:105:
/usr/include/errno.h:54: error: redundant redeclaration of '__errno'
/usr/include/signal.h:72: warning: previous declaration of '__errno' was here

Moving it to use COMPILER=base-clang ports-gcc fixes it.

ok?

(cc maintainer)

--Kurt

Index: Makefile
===================================================================
RCS file: /cvs/ports/graphics/graphene/Makefile,v
retrieving revision 1.13
diff -u -r1.13 Makefile
--- Makefile 24 Jun 2020 16:52:17 -0000 1.13
+++ Makefile 13 Nov 2020 15:53:12 -0000
@@ -21,6 +21,8 @@
MODULES= devel/meson \
x11/gnome

+COMPILER= base-clang ports-gcc
+
MODGNOME_TOOLS= gobject-introspection

LIB_DEPENDS= devel/glib2