Add an option to compile Hack TypeChecker only about homebrew-hhvm

[jwatzman]

A prerequisite to this would likely be changes to the HHVM cmake configuration so that we don't need the huge list of HHVM-only dependencies.

[Orvid]

The hack section of the cmake build searches for its dependencies separately from HHVM.

[jwatzman]

Yes, but there is no mechanism to configure one without the other AFAIK, it's all tangled together. Or does CMake have some magic?

[Orvid]

Adding SET(CMAKE_MODULE_PATH "${CMAKE_CURRENT_SOURCE_DIR}/../../CMake" ${CMAKE_MODULE_PATH}) before the find_package calls in hphp/hack/CMakeLists.txt and then just calling cmake . from hphp/hack/ should work just fine.

[Orvid]

Ideally it would be better to move the IF(HPHP_HOME) check out of the loop and use that as the base path for finding /CMake, but it's not required.

[jwatzman]

Ah, cool.

@raeesiqbal this isn't something I'm likely to have time to work on myself, but I'd be happy to review a PR to do it. (You'll need to update the CMake scripts in HHVM itself as above, then submit a change to the brew formula to take advantage of it.)

[RaeesBhatti]

I'm not familiar with Ruby and HomeBrew formulas, so, I tried a lot of things but could not make cmake inside the hphp/hack directory work.
We can't just cmake HHVM first and then Hack because that will require a lot of packages to be present that Hack doesn't need. Here are my finding:

• Hack requires lz4,libelf,ocaml to work, so, we can create a HomeBrew option with-hack-only and do a if not build.with? "hack-only" check on things which are not required by Hack.
• We can actually build Hack utilities on Mac using configure, cmake . and make in hphp/hack directory when you have the dependecies installed.

[fredemmott]

That referenced commit means this is now supported by hhvm itself, just not by brew. Would also like this so that when the hhvm build is broken by folly/clang/apple can hopefully keep using nuclide with local hh_client

[fredemmott]

For now, I'm wontfixing this, as we should have bottles up very shortly (#5)