build: avoid passing private flags from pmake
build: avoid passing private flags from pmake

pmake introduces private flags (-J) when passing certain arguments
to it (such as -j). Filter these out before passing to gmake.

PR-URL: https://github.com/iojs/io.js/pull/1334
Reviewed-By: Fedor Indutny <e39d94bae70283f13d24c278e04952d6dad9384b@indutny.com>

dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node,dreamllq/node