Add some simple deductions of --cc given --cc-bin
Add some simple deductions of --cc given --cc-bin

If --cc is not set but --cc-bin is, try guessing the compiler type
based on that.

This is useful for OSS-Fuzz (https://github.com/google/oss-fuzz/pull/649)
and convenient elsewhere (eg --cc-bin=afl-clang++ now does the right thing)

randombit/botan,Rohde-Schwarz-Cybersecurity/botan,webmaster128/botan,randombit/botan,Rohde-Schwarz-Cybersecurity/botan,Rohde-Schwarz-Cybersecurity/botan,randombit/botan,Rohde-Schwarz-Cybersecurity/botan,webmaster128/botan,randombit/botan,Rohde-Schwarz-Cybersecurity/botan,webmaster128/botan,Rohde-Schwarz-Cybersecurity/botan,webmaster128/botan,webmaster128/botan,randombit/botan