Rollup merge of #98418 - topjohnwu:macos-dylib, r=jyn514

Allow macOS to build LLVM as shared library

Inspired by how [homebrew](https://github.com/Homebrew/homebrew-core/blob/HEAD/Formula/llvm.rb) builds and distributes llvm, here we manually create a symlink with a versioned dylib path to make `llvm-config` work properly. Note, the resulting `rustc` executable and `librustc_driver-<hash>.dylib` still links to the un-versioned `libLLVM.dylib` as expected when distributed in the final output. I have confirmed this by checking `otool -L` on both binaries.

After the change, enabling `llvm.link-shared` and `llvm.thin-lto` will be possible on macOS.

1 files changed, 10 insertions, 6 deletions

diff --git a/src/bootstrap/lib.rs b/src/bootstrap/lib.rs
index 859d35b7d7b..40ff0381c8b 100644
--- a/src/bootstrap/lib.rs
+++ b/src/bootstrap/lib.rs
@@ -107,15 +107,11 @@ use std::cell::{Cell, RefCell};
 use std::collections::{HashMap, HashSet};
 use std::env;
 use std::fs::{self, File};
+use std::io;
 use std::path::{Path, PathBuf};
 use std::process::{self, Command};
 use std::str;
 
-#[cfg(unix)]
-use std::os::unix::fs::symlink as symlink_file;
-#[cfg(windows)]
-use std::os::windows::fs::symlink_file;
-
 use filetime::FileTime;
 use once_cell::sync::OnceCell;
 
@@ -1460,7 +1456,7 @@ impl Build {
                 src = t!(fs::canonicalize(src));
             } else {
                 let link = t!(fs::read_link(src));
-                t!(symlink_file(link, dst));
+                t!(self.symlink_file(link, dst));
                 return;
             }
         }
@@ -1585,6 +1581,14 @@ impl Build {
         iter.map(|e| t!(e)).collect::<Vec<_>>().into_iter()
     }
 
+    fn symlink_file<P: AsRef<Path>, Q: AsRef<Path>>(&self, src: P, link: Q) -> io::Result<()> {
+        #[cfg(unix)]
+        use std::os::unix::fs::symlink as symlink_file;
+        #[cfg(windows)]
+        use std::os::windows::fs::symlink_file;
+        if !self.config.dry_run { symlink_file(src.as_ref(), link.as_ref()) } else { Ok(()) }
+    }
+
     fn remove(&self, f: &Path) {
         if self.config.dry_run {
             return;