libclang output name is now libclang. This solves a name collision when building with Visual Studio. `clang.dll' and `clang.exe' would have the same `clang.ilk' and `clang.pdb'. On a serial build those files would be overwritten as clang.exe/clang.dll are created. On a parallel build there is a risk of both files being written at the same time. On that case VS fails.
libclang output name is now libclang. This solves a name collision
when building with Visual Studio. `clang.dll' and `clang.exe' would
have the same `clang.ilk' and `clang.pdb'. On a serial build those
files would be overwritten as clang.exe/clang.dll are created. On a
parallel build there is a risk of both files being written at the same
time. On that case VS fails.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@129239 91177308-0d34-0410-b5e6-96231b3b80d8

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