try to work around CI issue

Author: RalfJung

src/bootstrap/src/core/config/config.rs

@@ -2095,6 +2095,9 @@ impl Config {
     /// Use this rather than `Command::new("git")` in order to support out-of-tree builds.
     pub(crate) fn git(&self) -> Command {
         let mut git = Command::new("git");
+        git.current_dir(&self.src);
+        // Inside a git hook, just setting the working dir is not sufficient (probably because of
+        // some env vars). But CI failed if we only set `--git-dir` so we do both.
         git.arg("--git-dir").arg(self.src.join(".git"));
         git
     }