[Support] Support building LLVM for Fuchsia

These are necessary changes to support building LLVM for Fuchsia.
While these are not sufficient to run on Fuchsia, they are still
useful when cross-compiling LLVM libraries and runtimes for Fuchsia.

Differential Revision: https://reviews.llvm.org/D46345

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@331423 91177308-0d34-0410-b5e6-96231b3b80d8
2 files changed