[clang] [clang][driver] Allow unaligned access on ARMv7 and higher by default (PR #82400)

[Paul Kirth via cfe-commits]

ilovepi wrote:

> Hi - I like the change. We have this code in the downstream compiler, which also enables this for Armv6, but specifically disables it for v6m and v8m.baseline.
> 
> ```
>       if (VersionNum < 6 ||
>           Triple.getSubArch() == llvm::Triple::SubArchType::ARMSubArch_v6m ||
>           Triple.getSubArch() == llvm::Triple::SubArchType::ARMSubArch_v8m_baseline) {
>         Features.push_back("+strict-align");
>       }
> ```
> 
> I don't have a strong opinion about what happens with ARMv6, but this deserves a release note. And v6m/v8m.baseline probably deserve specific code and a test.

Those are good points, echoed by @smithp35. I'll update the patch accordingly.

Off hand, do either of you know if there are other differences in the driver that that we would want to consider adopting?

https://github.com/llvm/llvm-project/pull/82400