Add a buildifier warning to enforce rule load location

[styurin]

Addresses #1231, but without auto fixing.

[styurin]

@vladmos could you take a look, please?

[vladmos]

Is it actually recommended anywhere that genrule should be loaded from "//:genrule.bzl"? Imo it can be confusing for the users who have a different setup in their codebase.

Also, please fix the merge conflict.

[styurin]

Is it actually recommended anywhere that genrule should be loaded from "//:genrule.bzl"? Imo it can be confusing for the users who have a different setup in their codebase.

Updated to use "//tools/bazel:genrule.bzl" instead. This should promote better practices to structure folders with Bazel libraries.

[styurin]

@vladmos could you take another look, please?

[vladmos]

I'm sorry, I still don't understand where the recommendation come from. If that's been discussed e.g. in a mailing list, could you please attach a link? I can imagine that some smaller projects have their own code structure and enforcing a fixed load location without apparent upsides can be noisy. Besides, isn't "genrule" a built-in function that doesn't need to be loaded at all?