fix: Detect cc/c++ hard link to clang/clang++ before gcc/g++

fix: Detect cc/c++ hard link to clang/clang++ before gcc/g++

Apparently clang/clang++ can be gcc/g++ in addition to cc/c++, at least
on some macOS versions, so detect clang hard link before gcc since the
other way around (gcc installed as an alias of clang) seems less likely.

Fixes #1597.