CC check inconsistency between source and bindist configure scripts
The bindist configure script has:
```
AC_PROG_CC([gcc clang])
AC_PROG_CXX([g++ clang++ c++])
```
whereas the source configure script has:
```
AC_PROG_CC([cc gcc clang])
AC_PROG_CXX([g++ clang++ c++])
```
There are two issues here:
* the binary distribution check won't use `cc`
* both checks favor concrete C++ compilers rather than the generic `c++` executable
issue