[analyzer][scan-build] Non-existing directory for scan-build output.
[analyzer][scan-build] Non-existing directory for scan-build output.

Makes scan-build successfully accept non-existing output directories provided via "-o" option. The directory is created in this case. This behavior is conforming to the old perl scan-build implementation.
(http://reviews.llvm.org/D17091)

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@261480 91177308-0d34-0410-b5e6-96231b3b80d8
(cherry picked from commit 8f351cf9bd30e6c8bc2577ff85410ed557ca1b51)

apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang,apple/swift-clang