[X86] Enable shrink-wrapping for no-frame-pointer non-nounwind functions on...

[X86] Enable shrink-wrapping for no-frame-pointer non-nounwind functions on platforms not using compact unwind

The current compact unwind scheme does not work when the prologue is not at the
start (the instructions before the prologue cannot be described).  (Technically
this is fixable, but it requires multiple compact unwind descriptors for one
function.)

rL255175 chose to not perform shrink-wrapping for no-frame-pointer functions not
marked as nounwind to work around PR25614. This is overly limited, as platforms
not supporting compact unwind (all non-Darwin) does not need the workaround.
This patch restricts the limitation to compact unwind platforms.

Reviewed By: qcolombet

Differential Revision: https://reviews.llvm.org/D89930