cotire 1.6.4

Summary: Closes #3194
Created from: https://github.com/facebook/hhvm/pull/3194

Reviewed By: @ptarjan

Differential Revision: D1435738
unset another cached variable for dwarf detection

Summary: We're not actually broken right now because of the way we fall-back to
dwarf_producer_init_c, but a function exists check is still being
skipped due to CMake caching. That could potentially confuse things
if/when another init function were to be added in the future.
Closes #3200
Created from: https://github.com/facebook/hhvm/pull/3200

Reviewed By: @ptarjan

Differential Revision: D1438631
Fix CMake to install hh_client and hh_server

Summary: Make sure we install under bin/ the hack binaries.
Closes #3192
Closes #3158
Created from: https://github.com/facebook/hhvm/pull/3192

Reviewed By: @jwatzman

Differential Revision: D1435736