Support GCC and clang PCH use and multiple or chaining PCH
SCons currently support use of a single PCH file on msvc builds.
However it is possible to chain PCH files so that a given compile job will use a PCH which actually represent multple PCH files.
Also add support with GCC and clang toolchains. I created a POC tool which removed the common PCH code from msvc.py and mslink.py and put them to use in a tool which can be used with several compilers.
This branch contains the changes to scons and the tool: https://github.com/dmoody256/mongo/tree/pch_working
Pch tool file: https://github.com/dmoody256/mongo/blob/pch_working/site_scons/site_tools/pch.py
See also #1435
See also #2489
These are no longer available?