bundle: Restore local install on macOS (#41482)

I just pulled and ran a local build via `script/bundle-mac -l -i` but
found that the resulting bundle wasn't installed as expected. (me:
"ToggleAllDocks!! Wait! Where is it?!") Looking into, it looks like the
`-l` flag was removed in #41392, leaving the `$local_only` var orphaned,
which then left the `-i/$local_install` flag unreachable. I suspect that
this was unintentional, so this PR re-adds the `-l/$local_only` flag to
`script/bundle-mac`.

I ran the build again and confirmed that local install seemed to work as
expected. (ie "ToggleAllDocks!! 🎉")

While here, I also removed the last reference to `$local_arch`, because
all other references to that were removed in #41392.

/cc @osiewicz 

Release Notes:

- N/A

---------

Co-authored-by: Conrad Irwin <conrad.irwin@gmail.com>

tooling/xtask/src/tasks/workflows/run_tests.rs

@@ -25,7 +25,7 @@ pub(crate) fn run_tests() -> Workflow {
     let should_check_docs = PathCondition::new("run_docs", r"^docs/");
     let should_check_scripts = PathCondition::new(
         "run_action_checks",
-        r"^\.github/(workflows/|actions/|actionlint.yml)|tooling/xtask",
+        r"^\.github/(workflows/|actions/|actionlint.yml)|tooling/xtask|script/",
     );
     let should_check_licences =
         PathCondition::new("run_licenses", r"^(Cargo.lock|script/.*licenses)");