Two changes to scan-build:
Two changes to scan-build:

(1) When no 'clang' is found with 'scan-build', remember the one from
the path as scan-build sees it, not the build system.  This prevents
us from finding different clangs during the build.

(2) Don't set LDPLUSPLUS when running xcodebuild; instead rely on the
clang driver to do the right thing.



git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@95943 91177308-0d34-0410-b5e6-96231b3b80d8

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