IntelLLVM: Use MSVC linker with MSVC frontend variant

The Intel compiler (pre-LLVM) expected xilink.exe and had special logic to
set xilink.exe.  The newer LLVM-based compiler does not want xilink.exe.
link.exe works better for host code, and is the default, so change
the matching condition such that the old compiler matches (and gets
xilink.exe) and the new compiler gets the default link.exe it expects.

A better solution will be to use the compiler as the linker.  A future
change will switch to compiler as linker by default, but that fix needs
more validation.

Signed-off-by: William R. Dieter <william.r.dieter@intel.com>
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