Capture CMAKE_<LANG>_COMPILER_ARG1 from CMAKE_<LANG>_COMPILER in the
same fashion that it is from $ENV{<LANG>}.

Since get_filename_component() returns a single string of all the
arguments from $ENV{<LANG>}, a single string of arguments will be
constructed from the items contained in CMAKE_<LANG>_COMPILER.

Fixes #20089