Extender should throw when trying to bundle with incompatible bob version

[dapetcu21]

Is your feature request related to a problem? Please describe (REQUIRED):
I keep making the mistake of forgetting to change the build server URL between staging and production. The problem is that extender doesn't point out this mistake to me and instead tries to compile anyway and fails on some random missing files, resulting in an unhelpful error and a lot of headscratching.

Describe the solution you'd like (REQUIRED):
Extender should error out early if trying to compile with a version of bob for which it doesn't have a corresponding engine build on file.

Describe alternatives you've considered (REQUIRED):
Paying more attention, but that's not always achievable 😄. I usually remember the fix if I have the same problem twice, but this time I seem to have been fooled 3 times (that i can remember) already, since the errors tend to be different each time.

Additional context (OPTIONAL):
One instance in which I was fooled: defold/defold#4903

[britzl]

Need some input from @JCash here