[compiler-rt] [nsan] Use ALIGNED instead of alignas (NFC) (PR #98933)

[Fangrui Song via llvm-commits]

MaskRay wrote:

We already require support for `alignas` in some compiler-rt library files: `rg -w alignas compiler-rt/lib` (lsan, scudo, gwp_asan, xray, etc).
Old compilers can use `LLVM_ENABLE_RUNTIMES=compiler-rt`, which will use just built Clang to build the runtime libraries.

We could also make `COMPILER_RT_HAS_*` false when Clang is too old.

https://github.com/llvm/llvm-project/pull/98933