Turn off PIC for the JIT
It was added in 7723bd20b599af78ac975dbc7173f2e5effd0af9 to make TLS access work.
We have since changed how we do that and shouldn't need anything special from LLVM anymore.
This was useful to expose (and be affected by) LLVM bugs though
(i.e. https://reviews.llvm.org/D34409)
