Disarm drop bombs for unexecuted test Cargo commands

The code for running tests uses a custom command machinery because it streams the output of the command. We thus need to mark the command as executed in a dry run, to avoid a drop bomb panic.

src/bootstrap/src/utils/channel.rs

@@ -58,7 +58,7 @@ impl GitInfo {
 
         // Ok, let's scrape some info
         let ver_date = output(
-            &mut helpers::git(Some(dir))
+            helpers::git(Some(dir))
                 .arg("log")
                 .arg("-1")
                 .arg("--date=short")

src/bootstrap/src/utils/render_tests.rs

@@ -33,6 +33,7 @@ pub(crate) fn try_run_tests(
     stream: bool,
 ) -> bool {
     if builder.config.dry_run() {
+        cmd.mark_as_executed();
         return true;
     }