Avoid output file collisions on revisions

Author: oli-obk

examples_tests/rustc_basic/executable.rs

@@ -1,4 +1,5 @@
 //@run
+//@revisions: a b c d e f g h i j k l m n
 
 fn main() {
     std::thread::sleep(std::time::Duration::from_secs(5));

src/per_test_config.rs

@@ -136,6 +136,7 @@ impl TestConfig {
         cmd.arg(self.status.path());
         if !self.status.revision().is_empty() {
             cmd.arg(format!("--cfg={}", self.status.revision()));
+            cmd.arg(format!("-Cextra-filename={}", self.status.revision()));
         }
         for r in self.comments() {
             cmd.args(&r.compile_flags);

tests/integrations/basic-fail/Cargo.stdout

@@ -817,7 +817,7 @@ full stdout:
 
 
 FAILED TEST: tests/actual_tests_bless/revisions_bad.rs (revision `bar`)
-command: "rustc" "--error-format=json" "--out-dir" "$TMP "tests/actual_tests_bless/revisions_bad.rs" "--cfg=bar" "--extern" "basic_fail=$DIR/tests/integrations/basic-fail/../../../target/$TMP/$TRIPLE/debug/libbasic_fail.rlib" "--extern" "basic_fail=$DIR/tests/integrations/basic-fail/../../../target/$TMP/$TRIPLE/debug/libbasic_fail-$HASH.rmeta" "-L" "$DIR/tests/integrations/basic-fail/../../../target/$TMP/$TRIPLE/debug" "-L" "$DIR/tests/integrations/basic-fail/../../../target/$TMP/$TRIPLE/debug" "--edition" "2021"
+command: "rustc" "--error-format=json" "--out-dir" "$TMP "tests/actual_tests_bless/revisions_bad.rs" "--cfg=bar" "-Cextra-filename=bar" "--extern" "basic_fail=$DIR/tests/integrations/basic-fail/../../../target/$TMP/$TRIPLE/debug/libbasic_fail.rlib" "--extern" "basic_fail=$DIR/tests/integrations/basic-fail/../../../target/$TMP/$TRIPLE/debug/libbasic_fail-$HASH.rmeta" "-L" "$DIR/tests/integrations/basic-fail/../../../target/$TMP/$TRIPLE/debug" "-L" "$DIR/tests/integrations/basic-fail/../../../target/$TMP/$TRIPLE/debug" "--edition" "2021"
 
 error: ``main` function not found in crate `revisions_bad`` not found in diagnostics outside the testfile
  --> tests/actual_tests_bless/revisions_bad.rs:4:31