swift234

LIT: Hack the %libdir expansion once more, so it works with
- configure+make
- cmake+make
and (drumroll)
- cmake+xcode
The problem is that in XCode, swift_lib_dir will expand to
"lib/$(CONFIGURATION)$(EFFECTIVE_PLATFORM_NAME)". So apparently the only
safe solution is to use $(dirname %swift)/../lib.

Swift SVN r8520