Do not rebuild by default for speed

[sneurlax]

When working on Android, rebuilding tor for every platform every flutter run or build can slow development pace. Not rebuilding by default would save some time, especially for Android.

We might consider using debug mode to force rebuilds, and a full build should always happen the first time from a clean slate.

[sneurlax]

This is true for flutter_libsparkmobile as well as for the Tor plugin, but this issue's obviously unrelated to Tor :P I'm a victim of the copypasta