add github CI signal

Summary:
sapling github CI  had a failure on fb303 and I wasn't sure if fb303 was itself building ok on github,  so lets give fb303 a CI.

* add a github action to build fb303
* delete fb303 github side packit config [as it is broken](https://github.com/facebook/fb303/pull/58/checks?check_run_id=31169950255). For folly packit was moved to copr side in D54958528 so I think this is fine.

 (the underlying problem causing a transient [fb303 break in sapling CI](https://github.com/facebook/sapling/actions/runs/11213566522/job/31166881318?pr=963) was that build/deps/github_hashes/facebook/fbthrift-rev.txt was lagging the code using fbthrift, and thus python libs where not installed)

X-link: facebook/fb303#58
X-link: facebookincubator/zstrong#1006

Reviewed By: singhsrb

Differential Revision: D63976936

build/fbcode_builder/manifests/mononoke_integration

@@ -45,9 +45,3 @@ zstd
 
 [dependencies.os=linux]
 sqlite3
-
-[dependencies.os=darwin]
-gnu-bash
-gnu-coreutils
-gnu-grep
-gnu-sed