gallivm: Disable frame-pointer-omission on x86 to ensure right stack alignment.

gallivm: Disable frame-pointer-omission on x86 to ensure right stack alignment.

Between release 3.2 and 3.3 LLVM stopped aligning properly when certain
conditions (no allocas, but large number of vectors causing spills to
the stack, and frame pointer omission enabled).

We were already disabling frame-pointer-omission on several build types,
but we now disable it on all build types.

It's not clear whether this affects 32-bits x86 processes only, or if it
can also affect 64-bits x86_64 processes when AVX registers are
available and used.  So disable frame-pointer-omission on both
x86/x86_64 to be on the safe side.

See also:
- http://llvm.org/PR21435

Reviewed-by: Roland Scheidegger <sroland@vmware.com>