Auto merge of #79096 - pietroalbini:stable-build-manifest-newline, r=Mark-Simulacrum
build-manifest: strip newline from rustc version
While running the release process for Rust 1.48.0 I discovered a bug in `build-manifest`: it's not trimming the newline from `src/version`, and it tries to inspect tarballs called `rustc-1.48.0\n-x86_64-unknown-linux-gnu.tar.xz`. The bug only affects stable releases so this is why we're only seeing it right now.
r? `@Mark-Simulacrum`
We'll need to backport this to beta and nightly too.
