Clang may raise an error when passed a `-march=` option that doesn't
correspond to the current target triple. CMake cannot pass the target
triple when determining the compiler id because it doesn't know how yet,
but it does pass along user-specified flags. This breaks when those
user-specified flags include `-march=`. Fix this use case by also
trying to find the compiler id without the user-specified flags.
Fixes: #16587
At least one Fortran compiler does not provide a preprocessor symbol to
identify itself. Instead we try running unknown compilers with version
query flags known for each vendor and look for known output. Future
commits will add vendor-specific flags/output table entries.
