[OMPIRBuilder] Don't outline DISTRIBUTE on CPUs (#158317)
We use different OpenMP runtime functions on CPU and target offload. The
one used for DISTRIBUTE on target offload needs a function pointer to an
offloaded function, but the one on CPU doesn't. This caused unnessecary
overhead on CPUs because SHARED or FIRSTPRIVATE memory from the
surrounding context has to be packaged into a context structure just for
an ordinary function call (which would hopefully eventually get
inlined). This also makes the IR harder to read.
