Fix issue rust-lang#96943

Author: adaszko

Cargo.lock

@@ -3624,6 +3624,7 @@ dependencies = [
  "itertools",
  "jobserver",
  "libc",
+ "libloading",
  "object 0.28.4",
  "pathdiff",
  "regex",

compiler/rustc_codegen_ssa/Cargo.toml

@@ -19,6 +19,7 @@ pathdiff = "0.2.0"
 snap = "1"
 smallvec = { version = "1.6.1", features = ["union", "may_dangle"] }
 regex = "1.4"
+libloading = "0.7.1"
 
 rustc_serialize = { path = "../rustc_serialize" }
 rustc_arena = { path = "../rustc_arena" }

compiler/rustc_codegen_ssa/src/back/archive.rs

@@ -4,6 +4,7 @@ use rustc_session::Session;
 use rustc_span::symbol::Symbol;
 
 use std::io;
+use std::ffi::OsStr;
 use std::path::{Path, PathBuf};
 
 pub(super) fn find_library(
@@ -32,6 +33,17 @@ pub(super) fn find_library(
             if test.exists() {
                 return test;
             }
+            if cfg!(target_os = "macos") {
+                // This is a bit unintuitive: On macOS, a shared library may not be present on the file
+                // system yet still be loadable.  This is due to the fact that there's a global cache of shared libraries being
+                // maintained by the system on BigSur and newer [1].  Therefore, as a last resort, try loading the library
+                // instead of just checking for its existence as a file.
+                // [1]: https://web.archive.org/web/20220317152936/https://developer.apple.com/documentation/macos-release-notes/macos-big-sur-11-beta-release-notes
+                let path: &OsStr = test.as_ref();
+                if let Ok(_) = unsafe { libloading::Library::new(path) } {
+                    return test;
+                }
+            }
         }
     }
     sess.fatal(&format!(