Auto merge of #29431 - sagudev:mtry, r=jdm

Add try command to mach & try build partitioned

Adds `./mach try` command that enables anybody to easily test their changes without opening PR and requesting try from bors-servo, by force pushing HEAD to appropriate branch. Command accepts branches names to select only partial runs of CI (same like bors try command). So if you only want to test mac build (that would be `@bors-servo try=mac`) you run `./mach try mac`. If no job is specified, try branch is used.

As partitioned CI jobs were not working after migration to GitHub Actions I remade them by using if guards.
Also WPT jobs were failing due to empty `INTERMITTENT_TRACKER_DASHBOARD_SECRET` on my fork, so I added additional check to prevent failed run.

And that concludes my work on #29379 🎉

---
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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy` does not report any errors
- [x] These changes fix #29379

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- [ ] There are tests for these changes OR
- [x] These changes do not require tests because it's CI

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1 files changed, 1 insertions, 1 deletions

diff --git a/tests/wpt/servowpt.py b/tests/wpt/servowpt.py
index 477e00eb168..7766d19ff88 100644
--- a/tests/wpt/servowpt.py
+++ b/tests/wpt/servowpt.py
@@ -227,7 +227,7 @@ class TrackerDashboardFilter():
         self.headers = {
             "Content-Type": "application/json"
         }
-        if TRACKER_DASHBOARD_SECRET_ENV_VAR in os.environ:
+        if TRACKER_DASHBOARD_SECRET_ENV_VAR in os.environ and os.environ[TRACKER_DASHBOARD_SECRET_ENV_VAR]:
             self.url = f"{base_url}/dashboard/attempts"
             secret = os.environ[TRACKER_DASHBOARD_SECRET_ENV_VAR]
             self.headers["Authorization"] = f"Bearer {secret}"