forward env vars through tpx

Summary:
The migration to tpx broke Watchman's tests because test_bser relies on YARN_YARN_OFFLINE_MIRROR being set in the environment and tpx doesn't forward environment variables into the test.

Explicitly forward them ourselves.

Reviewed By: fanzeyi

Differential Revision: D27897172

fbshipit-source-id: 16c8017a89979802bd9d443825ed4e22cb6ff6c9

build/fbcode_builder/getdeps/builder.py

@@ -746,6 +746,10 @@ if __name__ == "__main__":
                     "--print-long-results",
                 ]
 
+            if tpx and env:
+                testpilot_args.append("--env")
+                testpilot_args.extend(f"{key}={val}" for key, val in env.items())
+
             if owner:
                 testpilot_args += ["--contacts", owner]