`abigen` and `setup_program_test` macros don't detect file changes

[segfault-magnet]

Incremental rust compilation will not recompile macros when the files used inside are changed.

Although this is still an open issue in Rust (see here) there might be a workaround to tie us over.

Unless fixed this might prove frustrating to users who are changing the contract/script code and have their compile fail because the macro didn't reevaluate (missing types, wrong contract ids, etc).