Restore lldb build
commit 6c10142251 ("Update LLVM submodule") disabled the lldb build.
This patch updates the lldb and clang submodules to once again build
against the LLVM that is included in the Rust tree, and reverts the
.travis.yml changes from that patch. T
Tom Tromey committed
289da84381cb227be7c7189c2ba704ac4f503664
Parent: 4efc0a7