[llvm] [MC,ELF] Emit warning if a string constant contains newline char. (PR #98060)

[Fangrui Song via llvm-commits]

MaskRay wrote:

subject

> `[MC,ELF] Emit warning if a string constant contains newline char.`

The convention is to omit the trailing period in the subject

https://github.com/llvm/llvm-project/pull/98060