Prevent probing of compilers that are not gcc, clang, or a variant #6314

We should add a verification that a compiler is probeable, and avoid any subsequent probe attempts if it is not. Currently, only gcc, clang, and variants of those, are probeable.

For example, if a user has a compile_commands.json that refers to a C/C++ compiler we do not support (i.e. gomacc.exe), we may probe it for each entry (if args differ, since we don't know what args are relevant), resulting in way too many, slow compiler-probe operations that will never succeed. We could use a single check to determine if a compiler is probeable or not. If not, we can avoid any subsequent probing of that executable.