flutter run --machine doesn't correctly stop/terminate if sent app.stop during build #16183
Description
If I try to terminate before the build has finished, I get back a response from the app.stop (and a message saying Application finished, but it carries on running and launches the app (resulting in a white paused screen, because I never connect to the debugger).
[14:02:24]: Spawning /Users/dantup/Dev/Google/flutter/bin/flutter with args ["run","--machine","-t","lib/main.dart","-d","E9DE19A9-CB73-48B2-8152-3912BAB91CB0","--start-paused"]
[14:02:24]: .. in /Users/dantup/Dev/Google/flutter/examples/stocks
[14:02:24]: .. in {"FLUTTER_HOST":"VSCode"}
[14:02:25]: <== [{"event":"app.start","params":{"appId":"beb6d2a6-ce0e-43cb-986c-8fb61953c7e8","deviceId":"E9DE19A9-CB73-48B2-8152-3912BAB91CB0","directory":"/Users/dantup/Dev/Google/flutter/examples/stocks","supportsRestart":true}}]
[14:02:26]: <== Launching lib/main.dart on iPhone X in debug mode...
[14:02:27]: ==> [{"id":"1","method":"app.stop","params":{"appId":"beb6d2a6-ce0e-43cb-986c-8fb61953c7e8"}}]
[14:02:27]: <== Application finished.
[14:02:27]: <== [{"id":"1","result":true}]
[14:02:31]: <== [{"event":"app.debugPort","params":{"appId":"beb6d2a6-ce0e-43cb-986c-8fb61953c7e8","port":8100,"wsUri":"ws://127.0.0.1:8100/ws","baseUri":"file:///Users/dantup/Library/Developer/CoreSimulator/Devices/E9DE19A9-CB73-48B2-8152-3912BAB91CB0/data/Containers/Data/Application/E4D448D4-5694-4A87-B302-D785B3315041/tmp/stocksZtBNGN/stocks/"}}]
[14:02:31]: <== [{"event":"app.progress","params":{"appId":"beb6d2a6-ce0e-43cb-986c-8fb61953c7e8","id":"0","progressId":null,"message":"Syncing files to device iPhone X..."}}]
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