[clang] [clang] Fix behavior of `__is_trivially_relocatable(volatile int)` (PR #77092)

[Nikolas Klauser via cfe-commits]

philnik777 wrote:

This isn't ABI breaking for us currently (at least in a non-benign way). We only use it to optimize `vector` growing currently, and just define it to `is_trivially_copyable` if `__is_trivially_relocatable` isn't available.

https://github.com/llvm/llvm-project/pull/77092