build for libffi assumes tar supports -z

[duncan]

cd libffi && /usr/bin/tar -zxf ../ghc-tarballs/libffi/libffi*.tar.gz
tar: z: unknown function modifier
Usage: tar {c|r|t|u|x}[BDeEFhilmnopPqTvw@[0-7]][bfk][X...] [blocksize] [tarfile] [size] [exclude-file...] {file | -I include-file | -C directory file}...
gmake[1]: *** [libffi/stamp.ffi.configure] Error 1

The libffi/ghc.mk uses

cd libffi && $(TAR) -zxf ../ghc-tarballs/libffi/libffi*.tar.gz

A quick grep indicates this is the only instance that assumes the -z flag. Other instances in the ghc build system that use tar do the compression separately, eg in ghc.mk:

"$(TAR)" chf - $(SRC_DIST_NAME) 2>$src_log | bzip2 >$(TOP)/$(SRC_DIST_TARBALL)

[duncan]

Spoke too soon, another instance in libraries/integer-gmp/gmp/ghc.mk

cd libraries/integer-gmp/gmp && $(TAR) -jxf ../../../$(GMP_TARBALL)

[igloo]

Fixed by:

Sun Feb 14 22:04:50 GMT 2010  Ian Lynagh <igloo@earth.li>
  * Don't rely on tar supporting -z; trac #3841

in the ghc repo, and:

Sun Feb 14 22:05:56 GMT 2010  Ian Lynagh <igloo@earth.li>
  * Don't rely on tar supporting -j; trac #3841

in the integer-gmp repo.

In both HEAD and 6.12.