Install libc++-dev on clang builds.
Install libc++-dev on clang builds.

PaulBussmann/cpputest,Mindtribe/cpputest,cpputest/cpputest,basvodde/cpputest,offa/cpputest,offa/cpputest,asgeroverby/cpputest,asgeroverby/cpputest,offa/cpputest,PaulBussmann/cpputest,basvodde/cpputest,Mindtribe/cpputest,KisImre/cpputest,basvodde/cpputest,Mindtribe/cpputest,PaulBussmann/cpputest,asgeroverby/cpputest,Mindtribe/cpputest,cpputest/cpputest,cpputest/cpputest,PaulBussmann/cpputest,KisImre/cpputest,cpputest/cpputest,basvodde/cpputest,asgeroverby/cpputest,KisImre/cpputest,offa/cpputest,KisImre/cpputest