Add regression test for compile data in alternate packages

[UebelAndre]

No description provided.

[martingms]

Ah, right. The relativize in utils.bzl actually does the "right thing", so if we s/paths.relativize/relativize/ on utils.bzl:870 you get the "right" path, but then we get Error in declare_file: the output artifact 'test/unit/compile_data/data/data.txt' is not under package directory 'test/unit/compile_data/src' for target '//test/unit/compile_data/src:lib' so I guess symlinking in those cases is not the right approach anyway. I'll look some more.

[martingms]

#3196 at least makes this build, but it's not enough I guess since the data.txt-file must also be symlinked (to the correct place) to actually be able to use it, which can't be done from that ctx without moving the symlink within the .../src package I guess? Or hm, I might be missing something since #3176 only extended the symlinking to include the compile_data, so how can this have worked before, when generated sources were still symlinked and built in the out tree?

[UebelAndre]

how can this have worked before, when generated sources were still symlinked and built in the out tree?

I updated the regression test to show how the data is consumed. This is exactly what how one of my targets was setup. I tend to not rely on relative paths for include_str.

[martingms]

Cool, glad the patch worked 👍