Set CMAKE_BUILD_WITH_INSTALL_RPATH for Fuchsia runtimes
Set CMAKE_BUILD_WITH_INSTALL_RPATH for Fuchsia runtimes

This doesn't make any difference since we don't use RPATH/RUNPATH
on Fuchsia but it avoids the CMake error when re-linking libraries
while building with Ninja.

Differntial Revision: https://reviews.llvm.org/D46610

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@331833 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,apple/swift-clang,apple/swift-clang,llvm-mirror/clang,llvm-mirror/clang,llvm-mirror/clang,apple/swift-clang,llvm-mirror/clang