Make: how to continue after a command fails?

Return successfully by blocking rm's returncode behind a pipe with the true command, which always returns 0 (success)

rm file || true

make -k (or --keep-going on gnumake) will do what you are asking for, I think.

You really ought to find the del or rm line that is failing and add a -f to it to keep that error from happening to others though.

Try the -i flag (or --ignore-errors). The documentation seems to suggest a more robust way to achieve this, by the way:

To ignore errors in a command line, write a - at the beginning of the line's text (after the initial tab). The - is discarded before the command is passed to the shell for execution.

For example,

clean:
  -rm -f *.o

This causes rm to continue even if it is unable to remove a file.

All examples are with rm, but are applicable to any other command you need to ignore errors from (i.e. mkdir).