sys-devel/gcc: ensure people do not use go or vtv on musl

profiles/base/package.use.mask

@@ -9,3 +9,9 @@ app-office/libreoffice branding
 # awilfox <awilfox@adelielinux.org> (23 Apr 2016)
 # GDB server is not compatible with musl.
 sys-devel/gdb server
+
+# awilfox <awilfox@adelielinux.org> (10 Jul 2016)
+# GCC Go requires ucontext, which is deprecated and has been removed from musl.
+# libvtv requires execinfo.h, which is not going to be implemented in musl:
+#     http://www.openwall.com/lists/musl/2015/04/09/3
+sys-devel/gcc go vtv