system/unzip: miscellaneous fixes
- Make sure CFLAGS are respected by setting LOCAL_UNZIP instead of LOCAL_ZIP and unsetting CFLAGS_OPT in the configure script.
- Don't strip too early by setting STRIP to a no-op and unsetting LFLAGS2 in the configure script.
- Cherry-pick a patch from Fedora to fix format warnings.
- Fix unzipsfx test on 32-bit arches by casting a literal argument to the correct type.