test/lit.cfg: Enhance getRegisteredTargets() to retrieve +Asserts.
test/lit.cfg: Enhance getRegisteredTargets() to retrieve +Asserts.

  - s/getRegisteredTargets/get_llc_props/g
  - get_llc_props() returns dict {"set_of_targets", "enable_assertions"}
  - Enable the feature "asserts".
    test/Driver/darwin-verify-debug.c had expected it.

git-svn-id: ffe668792ed300d6c2daa1f6eba2e0aa28d7ec6c@145231 91177308-0d34-0410-b5e6-96231b3b80d8

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