Switch to clang-r339409.

This also changes over llvm-strip to use the -o flag, rather than
relying on nonstandard (and no longer functional) positional arguments.

Bug: http://b/111998531
Test: Multiple new builds. For googlers - http://go/clang-r339409-testing
Change-Id: I8c82d06304af24a001e6552e36e2f540d8e364ce