com32: Per-object file LDFLAGS

com32: Per-object file LDFLAGS

Some object files need to link against the ELF libraries. Allow them
to be specified with the following syntax in the Makefiles,

     LDFLAGS_$(object_file) = $(LIBS)

By adding libraries in this way DT_NEEDED entries are created in the
ELF modules and the required library dependencies are automatically
loaded before running the module.

Signed-off-by: Matt Fleming <matt.fleming@intel.com>