Turn on CLANG_IS_CC when not building gcc

[Dimitry Andric]

On 2013-02-13 12:48, Dag-Erling Smørgrav wrote:> The following patches (for head and stable/9) automatically enable
> CLANG_IS_CC if GCC is disabled but CLANG is not.  Any objections?

This looks fine to me.  Otherwise, if ${CC} isn't set to clang,
buildworld might fail in mysterious ways... :)