Rollup merge of #111187 - krasimirgg:llvm-runtimes, r=jyn514

bootstrap: add llvm-project/runtimes to the sources

This is needed to build libunwind for LLVM 16:
https://discourse.llvm.org/t/runtimes-removed-support-for-llvm-enable-projects-in-libcxx-libcxxabi-and-libunwind/65707

Zulip thread: https://rust-lang.zulipchat.com/#narrow/stream/187780-t-compiler.2Fwg-llvm/topic/missing.20llvm-project.2Fruntimes.20in.20beta.20srcs

Checked by running `x.py dist` and verifying the produced source archive (build/dist/rustc-1.71.0-dev-src.tar.gz) contains the new directory.

src/bootstrap/dist.rs

@@ -822,6 +822,8 @@ fn copy_src_dirs(
             "llvm-project\\compiler-rt",
             "llvm-project/cmake",
             "llvm-project\\cmake",
+            "llvm-project/runtimes",
+            "llvm-project\\runtimes",
         ];
         if spath.contains("llvm-project")
             && !spath.ends_with("llvm-project")