Replace <TARGET> in CMAKE_<LANG>_COMPILE_OBJECT rule variables

In some languages the compiler may need to know the path of the final
target file for which an object is being compiled.  Honor the <TARGET>
placeholder for compilation rules to support such cases.

Note that this cannot work with OBJECT library targets because the final
target path is not known during compilation (there can even be more than
one final target).

Suggested-by: Vittorio Giovara <vittorio.giovara@gmail.com>
Merge topic 'compile-object-TARGET-placeholder' into next

0b7ad3f Replace <TARGET> in CMAKE_<LANG>_COMPILE_OBJECT rule variables