'realclean' cleans up all files specified in 'OBJECT'

Hi,
Using EU::MM-6.36.
On Win32, I've been doing stuff in a Makefile.PL like:

===========================
.
.
# If we're using an MS compiler we need to additionally link
# to MinGW's libgcc.a (for this particular module).
if($Config{cc} eq 'cl') {
  $hash{OBJECT} = '/full/path/to/libgcc.a';
}
WriteMakefile(%hash);
===========================

Unfortunately running 'nmake realclean' will now clean up libgcc.a ... which 
is not what I really wanted to happen.
I want 'realclean' to simply clean up all of the "derived files" - as per 
the documentation. I deduce that 'OBJECT' is therefore reserved for "derived 
files" and that there must be a better way to conditionally link to 
pre-existing libraries that have an extension that differs from 
$Config{lib_ext}.

How *should* I be doing it ?

Doing it with 'LIBS' is probably not all that straightforward as 
'-L/full/path/to -lgcc' will look for '/full/path/to/libgcc.lib' and fail to 
find '/full/path/to/libgcc.a'. (Note that $Config{lib_ext} is usually '.lib' 
when Sconfig{cc} is 'cl'.)

Cheers,
Rob