Cabal common stanzas get ignored for Android build of executables

[kmicklas]

Cabal common stanzas require an import as the first subfield of a component, e.g.

executable frontend
  import: default
  ...

This doesn't work with the sed script used to set up linking for Android. Weirdly Cabal doesn't seem to complain but just doesn't import the stanza. Although something more future-proof would be preferable, I believe this could be fixed by changing the script to match the import clause and preserving it before the stuff that gets added.

[Ericson2314]

This reminds me we ought to switch to using https://cabal.readthedocs.io/en/latest/developing-packages.html#foreign-libraries

[Ericson2314]

That further reminds me that if we want to better abstract over this stuff for the user, the program entry point should be some sort of backpack thing so you can write more libraries and things around it.