cmake: configure_linker_script: accept argument with file extension

Reduce the amount of {pre,post}fixing magic: I.e. let it be clearer at
call sites that "linker.cmd" is a file, rather than having to know that
"linker" will be postfixed with ".cmd" internally.

Change argument name to linker_script_gen, to better indicate that we
are producing a generated file.

No functional change expected.

Signed-off-by: Mark Ruvald Pedersen <mped@oticon.com>
1 file changed