Binary: Correct endian issue when cross-compiling
Binary: Correct endian issue when cross-compiling

Using `WORDS_BIGENDIAN` wasn't such a great idea after all!
When cross compiling host and target endianess may differ and
`WORDS_BIGENDIAN` refers to host endianess.

Reviewers: austin, bgamari, trofi

Reviewed By: bgamari, trofi

Subscribers: rwbarton, trofi, thomie

Differential Revision: https://phabricator.haskell.org/D3122

shlevy/ghc,sdiehl/ghc,sdiehl/ghc,sdiehl/ghc,ezyang/ghc,shlevy/ghc,ezyang/ghc,shlevy/ghc,ezyang/ghc,sdiehl/ghc,sdiehl/ghc,shlevy/ghc,ezyang/ghc,shlevy/ghc,ezyang/ghc,ezyang/ghc,shlevy/ghc,sdiehl/ghc,ezyang/ghc,sdiehl/ghc,shlevy/ghc