* Detection of 64-bit Arm v8-a
* Proper detection of integer division support
* always on v7-m, v8-a, v9-a, v8-m.main
* sometimes on v7-a, v7-r, v8-r
* never on v8-m.base v6-m, v6 and older "classic"
* tl;dr: Rely on toolchain preprocessor definition
For the most part these additional variations won't acutally work
for native target builds, but sane -A detection is needed for
"local" builds now. -R detection is left out as it's not likely
to matter.
Change-Id: I8f6a52edc4d14490fc00e2f487406eca701eef02