How to disable CLANG & co build in buildworld?

[M. Warner Losh]

In message: <20100611185237.GL56080 at hoeg.nl>
            Ed Schouten <ed at 80386.nl> writes:
: Hello Andreas,
: 
: * Andreas Tobler <andreast-list at fgznet.ch> wrote:
: > I have a sparc64 machine which is quite slow. And for my purpose I
: > do not need CLANG etc. atm.
: 
: Clang is not enabled on sparc64, so there is no need to disable
: anything. If you do want to disable Clang on i386, amd64, pc98 or
: powerpc, add WITHOUT_CLANG=yes to /etc/src.conf, as described in
: src.conf(5).

Except that clang isn't quite disabled when cross-building, due to the
issue I pointed out when the commit went in wrt bsd.own.mk.
MACHINE_ARCH is still amd64 until we start to build the sparc64
binaries, so anything in the bootstrapping part of the build will not
be disabled.  that's one of many reasons disabling things in
bsd.own.mk based on architecture is going to fail.

Warner