Update folly
Remove the need for anchor-syms.cpp

Apply --whole-archive to hphp_runtime_static (Linux)
Apply -all_load to linker (MacOSX)
Call objcopy only once

On Linux, a trivial recompile, e.g.

  touch random-file.cpp; make

is sped up, for me, by 60% (going from 10m to 4m).