feat!: on Windows, also instruct msys to create real symlinks (#1443)

This will only reliably work on with developer setups, but that
seems fair to assume.
If this causes problems, it's fine to make it opt-in as well.

tests/tools/src/lib.rs

@@ -590,13 +590,16 @@ fn configure_command<'a>(
     script_result_directory: &Path,
 ) -> &'a mut std::process::Command {
     let never_path = if cfg!(windows) { "-" } else { ":" };
+    let mut msys_for_git_bash_on_windows = std::env::var("MSYS").unwrap_or_default();
+    msys_for_git_bash_on_windows.push_str(" winsymlinks:nativestrict");
     cmd.args(args)
         .stdout(std::process::Stdio::piped())
         .stderr(std::process::Stdio::piped())
         .current_dir(script_result_directory)
         .env_remove("GIT_DIR")
         .env_remove("GIT_ASKPASS")
         .env_remove("SSH_ASKPASS")
+        .env("MSYS", msys_for_git_bash_on_windows)
         .env("GIT_CONFIG_SYSTEM", never_path)
         .env("GIT_CONFIG_GLOBAL", never_path)
         .env("GIT_TERMINAL_PROMPT", "false")