Add to imports bin_dir so generated files can be propertly handled

[tomaszstrejczek]

Current implementation doesn't handle libraries which are generated via different rules (for example genrule) because files generated this way are stored in ctx.bin_dir directory which is not added as an import location. The PR adds to import ctx.bin_dir.

[Globegitter]

@tomaszstrejczek thanks for the contribution - can you please add a test that verifies this behaviour?

[sparkprime]

I'm not sure this is still relevant? It is very old.