[PATCHv2] Add support for LLVM_LIBDIR_SUFFIX.

Why?

-eric

Why?

-eric

Because openSUSE and many other linux distributions put all things to /usr/lib (i586) and /usr/lib64 (x86_64) or /usr/lib32.
So it is possible to install x86 and x86_64 versions at the same time ...
(See also http://lists.cs.uiuc.edu/pipermail/llvmdev/2011-July/042068.html and http://llvm.org/bugs/show_bug.cgi?id=10836)