Remove "-f" from autoreconf invocation

While working on adding fuzzer support I ran into errors which didn't cause the "autoreconf" program to fail, leaving me to work with outdated files until I noticed. This was caused by the "-f" ("--force") flag. There shouldn't be a need for that flag in pristine source trees.

fuzzing/Makefile.am:7: error: 'standalone.a' is not a standard library name
fuzzing/Makefile.am:7: did you mean 'libstandalone.a'?
fuzzing/Makefile.am: installing './depcomp'