[tlbuild] gcc vs. clang in icu

[Karl Berry]

    If patching ICU's configure.in is a possibility, I suggest we do so.

Anything's possible, but everything takes time, and since we seem to
have achieved a working-if-not-optimal configuration, I'm loath to
tinker with it.

If we did tinker, I'd be inclined to make it possible to manually
override ICU's choice of compiler (the way it should have been in the
first place).

    it will insist on using clang regardless 

Ah yes, I failed to see that it is only checking for the presence of an
executable, not whether the executable works.  Well, have to temporarily
rename the /usr/bin/clang(++), or wherever it is, to avoid it then :).

Thanks,
k