configure: Don't nuke Makefile if makedep is interrupted.
I noticed that if I Ctrl-C while makedep is re-generating the Makefile, the Makefile will be gone.
There are two parts to this problem:
- make deletes the output file if a rule is interrupted.
- Solution: use the special .PRECIOUS target.
- wine_fn_output_makefile overwrites the existing Makefile, because makedep
is hardcoded to use the output makefile as its input.
- Solution: add a -i command line options to makedep for specifying the input file name, then don't overwrite Makefile in wine_fn_output_makefile.