Avoid redundant rm in compile mode, fix locking.

Avoid redundant rm in compile mode, fix locking.

* libltdl/config/ltmain.m4sh (func_mode_compile): Avoid
redundant removal of old output files before compilation.
Do not remove $obj until we have successfully grabbed the
lockfile (in case the compiler doesn't grok `-c -o'), because
it might be identical to $output_obj.
At the end of the function, before we remove the lockfile,
update $removelist so that if the trap hits after the lockfile
has been removed, we do not accidentally remove $output_obj that
does not belong to us.
(func_write_libtool_object): Use $MV instead of mv.

Signed-off-by: Ralf Wildenhues <Ralf.Wildenhues@gmx.de>