Bootstrap make -- tries to compile c++ too soon

[Donn Terry]

The change by HJL on 5/20 to cp/Make-lang.in causes c++ to be made
too soon (even with LANGUAGES=c  (only)).  In my case, the compiler
options used for C++ are incompatible with the bootstrap compiler, and
this change introduces a dependency on the C++ compiler actually
having been built.  The rule body clearly is testing for whether LANGUAGES
intends to include C++, but the dependency is too strong.
 
Thanks in advance for looking into this.
 
Donn