Auto merge of rust-lang#8290 - ehuss:fix-lld-freshness, r=alexcrichton

Fix fingerprinting for lld on Windows with dylib.

This fixes an issue where if `lld` is used on Windows, dynamic libraries will never be treated as "fresh". This is a regression from rust-lang#8210 where Cargo is expecting export files to be created, but lld does not create these.

The solution is to ignore "Auxiliary" files in fingerprinting, which AFAIK aren't really needed (only the primary output files really matter).

Fixes rust-lang#8284

src/cargo/core/compiler/fingerprint.rs

@@ -1229,7 +1229,7 @@ fn calculate_normal(cx: &mut Context<'_, '_>, unit: &Unit) -> CargoResult<Finger
     let outputs = cx
         .outputs(unit)?
         .iter()
-        .filter(|output| output.flavor != FileFlavor::DebugInfo)
+        .filter(|output| !matches!(output.flavor, FileFlavor::DebugInfo | FileFlavor::Auxiliary))
         .map(|output| output.path.clone())
         .collect();
 

tests/testsuite/freshness.rs

@@ -2436,3 +2436,39 @@ fn linking_interrupted() {
         )
         .run();
 }
+
+#[cargo_test]
+#[cfg_attr(
+    not(all(target_arch = "x86_64", target_os = "windows", target_env = "msvc")),
+    ignore
+)]
+fn lld_is_fresh() {
+    // Check for bug when using lld linker that it remains fresh with dylib.
+    let p = project()
+        .file(
+            ".cargo/config",
+            r#"
+                [target.x86_64-pc-windows-msvc]
+                linker = "rust-lld"
+                rustflags = ["-C", "link-arg=-fuse-ld=lld"]
+            "#,
+        )
+        .file(
+            "Cargo.toml",
+            r#"
+                [package]
+                name = "foo"
+                version = "0.1.0"
+
+                [lib]
+                crate-type = ["dylib"]
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .build();
+
+    p.cargo("build").run();
+    p.cargo("build -v")
+        .with_stderr("[FRESH] foo [..]\n[FINISHED] [..]")
+        .run();
+}