[LLVMdev] Using thin archives when building llvm

[Rafael Espíndola]

> The Modules/Platform/Windows-MSVC.cmake module unconditionally
> sets CMAKE_CXX_CREATE_STATIC_LIBRARY and uses CMAKE_LINKER.
> As mentioned earlier the CMAKE_<LANG>_CREATE_STATIC_LIBRARY
> and similar variables are internal implementation details
> that are not meant to be set by users or project code.  That
> is why the above works only on certain platforms.
>
> Will thin archive support be distributed as part of llvm-ar
> proper for general use or is this only for LLVM's own build?
> If it will be for general use then it may also be worthwhile
> teaching CMake this option directly.

It is generally useful. The gnu ar already supports it. The
implementation in llvm-ar is compatible with it.

Making it available in llvm-lib is an extension over lib.exe.

Cheers,
Rafael