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

[David Green via cfe-commits]

davemgreen 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.

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