IR: Change clang to set -preserve-bc-uselistorder
Change clang to set -preserve-bc-uselistorder for the driver options
-emit-llvm and -save-temps. The former is useful for reproducing
results from clang in opt or llc, while the latter prevents
-save-temps from affecting the output. This is part of PR5680.
-preserve-bc-uselistorder=true is currently on by default, but a
follow-up commit in LLVM will reverse it.