Merge branch 'update-llvm' of https://github.com/alexcrichton/rust into update-cargo

llvm @ 0903c72c

-Subproject commit ba2edd794c7def715007931fcd1b4ce62aa711c8
+Subproject commit 0903c72cbbc3dafcb5c88820e4a8a98c3a764cf3

src/rustllvm/llvm-rebuild-trigger

 # If this file is modified, then llvm will be (optionally) cleaned and then rebuilt.
 # The actual contents of this file do not matter, but to trigger a change on the
 # build bots then the contents should be changed so git updates the mtime.
-2018-02-09
+2018-03-06