Track panic mode in fingerprint

Ensure that if we've previously compiled a crate with panic=abort and we later
need it for panic=unwind we correctly recompile it.

Closes #5445

Author: alexcrichton

src/cargo/core/compiler/fingerprint.rs

@@ -457,6 +457,7 @@ fn calculate<'a, 'cfg>(
         unit.mode,
         cx.extra_args_for(unit),
         cx.incremental_args(unit)?,
+        cx.used_in_plugin.contains(unit), // used when passing panic=abort
     ));
     let fingerprint = Arc::new(Fingerprint {
         rustc: util::hash_u64(&cx.build_config.rustc.verbose_version),

tests/testsuite/freshness.rs

@@ -1119,3 +1119,48 @@ fn path_dev_dep_registry_updates() {
         execs().with_status(0).with_stderr("[FINISHED] [..]"),
     );
 }
+
+#[test]
+fn change_panic_mode() {
+    let p = project("p")
+        .file(
+            "Cargo.toml",
+            r#"
+                [workspace]
+                members = ['foo', 'bar']
+                [profile.dev]
+                panic = 'abort'
+            "#,
+        )
+        .file("src/lib.rs", "")
+        .file(
+            "foo/Cargo.toml",
+            r#"
+                [package]
+                name = "foo"
+                version = "0.1.1"
+                authors = []
+            "#,
+        )
+        .file("foo/src/lib.rs", "")
+        .file(
+            "bar/Cargo.toml",
+            r#"
+                [package]
+                name = "bar"
+                version = "0.1.1"
+                authors = []
+
+                [lib]
+                proc-macro = true
+
+                [dependencies]
+                foo = { path = '../foo' }
+            "#,
+        )
+        .file("bar/src/lib.rs", "extern crate foo;")
+        .build();
+
+    assert_that(p.cargo("build -p foo"), execs().with_status(0));
+    assert_that(p.cargo("build -p bar"), execs().with_status(0));
+}