util: Enable neon when building arm/thumb versions of the m5 util.
Apparently the presence of a hardware FPU is no longer implied by
-march=armv7-a (or armv7 I assume), and so adding -mfpu=neon is
necessary when using hardware floating point in gcc/g++.
Change-Id: I59c5b58933fae2e4e5a747b2af128b801acc812e
Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/27747
Maintainer: Gabe Black <gabeblack@google.com>
Tested-by: kokoro <noreply+kokoro@google.com>
Reviewed-by: Jason Lowe-Power <power.jg@gmail.com>