This fixes an intermittent crash in `OpenMP` taskloop lowering.
In `OMPIRBuilder::createTaskloop`, the `restoreIP` in `PostOutlineCB`
was immediately overwritten by the following
`Builder.SetInsertPoint(StaleCI)` with no instructions created in
between, so it was effectively dead. This patch removes that dead
restore, which is the smallest change and preserves the intended IR
placement.
Adds a regression test that compiles a taskloop to LLVM IR and verifies
the bounds casts and __kmpc_taskloop call are present.
665c2e91e2