[clang] [Clang] Don't use crtbegin/crtend when building for musl. (PR #85089)

[Alastair Houghton via cfe-commits]

al45tair wrote:

(I had assumed that they came from the C library, since that's where `crt1.o` comes from, but if they don't then it sounds like I just need to build them.)

https://github.com/llvm/llvm-project/pull/85089