Revert "auto merge of #8695 : thestinger/rust/build, r=pcwalton"

This reverts commit 2c0f9bd35493def5e23f0f43ddeba54da9d788b4, reversing
changes made to f8c4f0ea9c96218dbc81081799e77875fbb071de.

Conflicts:
	src/rustllvm/RustWrapper.cpp
auto merge of #8838 : brson/rust/rvfpelim, r=alexcrichton

This reverts commit 2c0f9bd35493def5e23f0f43ddeba54da9d788b4, reversing
changes made to f8c4f0ea9c96218dbc81081799e77875fbb071de.

Conflicts:
	src/rustllvm/RustWrapper.cpp

Fixes #8833