npm repository tarball does not work with gnu-tar

[ddopson]

npm ERR! tar "-mvxpf" "-" "-o" "-C" "/tmp/npm-1320713133858/1320713133967-0.6399423768743873/contents/___package.npm" tar: Ignoring unknown extended header keyword LIBARCHIVE.creationtime' npm ERR! tar "-mvxpf" "-" "-o" "-C" "/tmp/npm-1320713133858/1320713133967-0.6399423768743873/contents/___package.npm" tar: Ignoring unknown extended header keywordSCHILY.dev'
npm ERR! tar "-mvxpf" "-" "-o" "-C" "/tmp/npm-1320713133858/1320713133967-0.6399423768743873/contents/___package.npm" tar: Ignoring unknown extended header keyword SCHILY.ino' npm ERR! tar "-mvxpf" "-" "-o" "-C" "/tmp/npm-1320713133858/1320713133967-0.6399423768743873/contents/___package.npm" tar: Ignoring unknown extended header keywordSCHILY.nlink'
npm ERR! tar "-mvxpf" "-" "-o" "-C" "/tmp/npm-1320713133858/1320713133967-0.6399423768743873/contents/___package.npm" tar: Ignoring unknown extended header keyword SCHILY.dev' npm ERR! tar "-mvxpf" "-" "-o" "-C" "/tmp/npm-1320713133858/1320713133967-0.6399423768743873/contents/___package.npm" tar: Ignoring unknown extended header keywordSCHILY.ino'
npm ERR! tar "-mvxpf" "-" "-o" "-C" "/tmp/npm-1320713133858/1320713133967-0.6399423768743873/contents/___package.npm" tar: Ignoring unknown extended header keyword `SCHILY.nlink'

Typically, this happens when the tarball has been built on MacOS, which runs bsdtar by default. Installing gnu-tar on mac and preferentially using that addresses the issue, as does building on a linux box. eg, "brew install gnu-tar; rm /usr/bin/tar; ln -s which gtar /usr/bin/tar"