Ben Gamari authored Feb 26, 2017 and Ben Gamari committed Feb 26, 2017

The build system uses the CrossCompiling variable to decide whether or
not we should build various packages that must be built using the
compiler.  Consequently, it is important that we persist its value in
the binary distribution so we know during `make install` not to go
looking for files that would have been built for these packages. Failing
to do this causes #13325.

Test Plan: Cross compile, `make binary-dist`, and try installing the
binary distribution on the target

Reviewers: hvr, austin, trofi, rwbarton

Reviewed By: trofi, rwbarton

Subscribers: carter, trofi, rwbarton, erikd, thomie, snowleopard, davean

Differential Revision: https://phabricator.haskell.org/D3187