[compiler-rt] fix(compiler-rt/**.py): fix invalid escape sequences (PR #94030)

[Eisuke Kawashima via llvm-commits]

e-kwsm wrote:

`\d`, `\(` and `\)` are not valid escape sequences; since python 3.12 
 they give SyntaxWarning, and will raise SyntaxError in future. <https://docs.python.org/3.12/whatsnew/3.12.html#other-language-changes>

`r"\(\d\)"` and `"\\(\\d\\)"` are equivalent but the former is the shorter.

https://github.com/llvm/llvm-project/pull/94030