[clang] [Sema] Fix format-strings test on 32-bit Arm (PR #178450)

[Leandro Lupori via cfe-commits]

luporl wrote:

@azhan92 It should be fixed by https://github.com/llvm/llvm-project/pull/180566.
Unfortunately, the code snippet above doesn't work for ARMv7.
The condition was getting too complicated, so I just skipped the warnings for 32-bit Arm.

https://github.com/llvm/llvm-project/pull/178450