Mark x11/xcolor BROKEN-sparc64

This port has never compiled on sparc64. Almost certainly because it calls
out an ancient version of the rust libc that has caused problems on sparc64
in the past. (See history of www/newboat).

I tried seeing if I could get it to use a newer version of libc, but after
lots of fighting to get it to even consider a newer version, is still
failed to build.

So this just marks it BROKEN-sparc64.

ok?

--Kurt

Index: Makefile
===================================================================
RCS file: /cvs/ports/x11/xcolor/Makefile,v
retrieving revision 1.2
diff -u -p -r1.2 Makefile
--- Makefile 14 Sep 2020 19:40:21 -0000 1.2
+++ Makefile 14 Sep 2020 22:07:50 -0000
@@ -1,5 +1,7 @@
# $OpenBSD: Makefile,v 1.2 2020/09/14 19:40:21 jasper Exp $

+BROKEN-sparc64 = "error[E0412]: cannot find type c_char in this scope"
+
COMMENT = lightweight color picker

GH_ACCOUNT = Soft