Rollup merge of #139721 - dtolnay:stage0newline, r=onur-ozkan

End all lines in src/stage0 with trailing newline

Most tools that process text files prefer if every line ends in \n. Text files without the last newline are aberrant and usually not what you want.

**Before:**

```console
$ cat src/stage0 src/stage0
dist_server=https://static.rust-lang.org
artifacts_server=https://ci-artifacts.rust-lang.org/rustc-builds
...
dist/2025-04-02/rustc-nightly-x86_64-unknown-netbsd.tar.gz=986f6c594d37bcbd3833e053640ba8775f68d26a65c5618386654ef55d7b3542
dist/2025-04-02/rustc-nightly-x86_64-unknown-netbsd.tar.xz=c0d9a88c30d2ab38ec3a11fabb5515ed9bc3ac1a8e35a438d68bf7ff82f6b843dist_server=https://static.rust-lang.org
artifacts_server=https://ci-artifacts.rust-lang.org/rustc-builds
...
dist/2025-04-02/rustc-nightly-x86_64-unknown-netbsd.tar.gz=986f6c594d37bcbd3833e053640ba8775f68d26a65c5618386654ef55d7b3542
dist/2025-04-02/rustc-nightly-x86_64-unknown-netbsd.tar.xz=c0d9a88c30d2ab38ec3a11fabb5515ed9bc3ac1a8e35a438d68bf7ff82f6b843$ ▌
```

**After:**

```console
$ cat src/stage0 src/stage0
dist_server=https://static.rust-lang.org
artifacts_server=https://ci-artifacts.rust-lang.org/rustc-builds
...
dist/2025-04-02/rustc-nightly-x86_64-unknown-netbsd.tar.gz=986f6c594d37bcbd3833e053640ba8775f68d26a65c5618386654ef55d7b3542
dist/2025-04-02/rustc-nightly-x86_64-unknown-netbsd.tar.xz=c0d9a88c30d2ab38ec3a11fabb5515ed9bc3ac1a8e35a438d68bf7ff82f6b843
dist_server=https://static.rust-lang.org
artifacts_server=https://ci-artifacts.rust-lang.org/rustc-builds
...
dist/2025-04-02/rustc-nightly-x86_64-unknown-netbsd.tar.gz=986f6c594d37bcbd3833e053640ba8775f68d26a65c5618386654ef55d7b3542
dist/2025-04-02/rustc-nightly-x86_64-unknown-netbsd.tar.xz=c0d9a88c30d2ab38ec3a11fabb5515ed9bc3ac1a8e35a438d68bf7ff82f6b843
$ ▌
```