Auto merge of rust-lang#122596 - rcxdude:master, r=petrochenkov

Use MSVC-style escaping when passing a response/@ file to lld on windows

LLD parses @ files like the command arguments on the platform it's on, so on windows it needs to follow the MSVC style to work correctly. Otherwise builds can fail if the linker command gets too long and the build path contains spaces.

compiler/rustc_codegen_ssa/src/back/command.rs

@@ -100,12 +100,6 @@ impl Command {
             Program::Lld(ref p, flavor) => {
                 let mut c = process::Command::new(p);
                 c.arg("-flavor").arg(flavor.as_str());
-                if let LldFlavor::Wasm = flavor {
-                    // LLVM expects host-specific formatting for @file
-                    // arguments, but we always generate posix formatted files
-                    // at this time. Indicate as such.
-                    c.arg("--rsp-quoting=posix");
-                }
                 c
             }
         };

compiler/rustc_codegen_ssa/src/back/link.rs

@@ -785,7 +785,7 @@ fn link_natively<'a>(
     let mut i = 0;
     loop {
         i += 1;
-        prog = sess.time("run_linker", || exec_linker(sess, &cmd, out_filename, tmpdir));
+        prog = sess.time("run_linker", || exec_linker(sess, &cmd, out_filename, flavor, tmpdir));
         let Ok(ref output) = prog else {
             break;
         };
@@ -1576,6 +1576,7 @@ fn exec_linker(
     sess: &Session,
     cmd: &Command,
     out_filename: &Path,
+    flavor: LinkerFlavor,
     tmpdir: &Path,
 ) -> io::Result<Output> {
     // When attempting to spawn the linker we run a risk of blowing out the
@@ -1584,9 +1585,9 @@ fn exec_linker(
     //
     // Here we attempt to handle errors from the OS saying "your list of
     // arguments is too big" by reinvoking the linker again with an `@`-file
-    // that contains all the arguments. The theory is that this is then
-    // accepted on all linkers and the linker will read all its options out of
-    // there instead of looking at the command line.
+    // that contains all the arguments (aka 'response' files).
+    // The theory is that this is then accepted on all linkers and the linker
+    // will read all its options out of there instead of looking at the command line.
     if !cmd.very_likely_to_exceed_some_spawn_limit() {
         match cmd.command().stdout(Stdio::piped()).stderr(Stdio::piped()).spawn() {
             Ok(child) => {
@@ -1606,8 +1607,12 @@ fn exec_linker(
     let mut args = String::new();
     for arg in cmd2.take_args() {
         args.push_str(
-            &Escape { arg: arg.to_str().unwrap(), is_like_msvc: sess.target.is_like_msvc }
-                .to_string(),
+            &Escape {
+                arg: arg.to_str().unwrap(),
+                // LLD also uses MSVC-like parsing for @-files by default when running on windows hosts
+                is_like_msvc: sess.target.is_like_msvc || (cfg!(windows) && flavor.uses_lld()),
+            }
+            .to_string(),
         );
         args.push('\n');
     }