Let build/tools/build-cxx-stl.sh now use ninja instead of make.

Makes building libcxx about 2s faster, and has a nicer UI.

Change-Id: I12d227b890dbe39f91e4d792537336705c0003fd

Conflicts:
	build/tools/build-cxx-stl.sh
Fix merge mistakes to bring to ToT include losing gabi++ fixes and build issues

Change-Id: Ie0d5f7b93f1e9896720ee9a5c95c13e94ffe179e
Use hermetic ar in llvm mode, just like with gcc.

Before this change, builder-funcs would use the host ar in llvm mode,
and the system ar on OS X doesn't understand all the flags that
builder-funcs writes.  Instead, use the ar binary from the hermetic
toolchain in llvm mode.

Change-Id: Ie65e510aba263f1d29af99a4d48996484ce00992

Conflicts:
	build/tools/builder-funcs.sh