Fix for PR3246: an empty clobber list is the empty string, not a null  string.
Fix for PR3246: an empty clobber list is the empty string, not a null 
string.

That said, we should probably try and track down the correct clobber 
lists for the targets that don't have them (PPC, ARM, and Sparc), 
so that we can generate correct code.



git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@61298 91177308-0d34-0410-b5e6-96231b3b80d8

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