Fixes for standalone build:
Fixes for standalone build:

* include CheckAtomic to set HAVE_CXX_ATOMICS64_WITHOUT_LIB properly (introduced in r274121)
* hint Clang CMake files for LLVM CMake files location (inctroduced in ~ r274176)

Differential revision: https://reviews.llvm.org/D22322


git-svn-id: 4c4cc70b1ef44ba2b7963015e681894188cea27e@275641 91177308-0d34-0410-b5e6-96231b3b80d8

apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,apple/swift-lldb,llvm-mirror/lldb,llvm-mirror/lldb,apple/swift-lldb,apple/swift-lldb