Remove j2objc_dead_code_pruner from rules_apple

[erikkerber]

Speculative fix for #2497

Appears j2objc_dead_code_pruner related code was removed from Bazel in bazelbuild/bazel@208b9c6

[mattrobmattrob]

Can you change or remove the name of _j2objc_binary_linking_attrs and all associated j2objc references?

[erikkerber]

@mattrobmattrob I can, if it's still the right thing to do. I don't know much of anything about j2objc, but the j2objc fragment is still needed from core:

ERROR: /Users/ekerber/Developer/rules_apple/test/starlark_tests/targets_under_test/ios/BUILD:1889:14: in ios_framework rule //test/starlark_tests/targets_under_test/ios:fmwk_stripped:
Traceback (most recent call last):
        File "/Users/ekerber/Developer/rules_apple/apple/internal/ios_rules.bzl", line 931, column 65, in _ios_framework_impl
                link_result = linking_support.register_binary_linking_action(
        File "/Users/ekerber/Developer/rules_apple/apple/internal/linking_support.bzl", line 243, column 58, in _register_binary_linking_action
                linking_outputs = apple_common.link_multi_arch_binary(
        File "/virtual_builtins_bzl/common/objc/linking_support.bzl", line 277, column 86, in _link_multi_arch_binary
        File "/virtual_builtins_bzl/common/objc/compilation_support.bzl", line 835, column 62, in _register_configuration_specific_link_actions
        File "/virtual_builtins_bzl/common/objc/compilation_support.bzl", line 605, column 26, in _register_j2objc_dead_code_removal_actions
Error: ios_framework has to declare 'j2objc' as a required fragment in order to access it. Please update the 'fragments' argument of the rule definition (for example: fragments = ["j2objc"])

As for the name of the Starlark macro holding _dummy_lib and _xcrunwrapper, those are needed IIUC for Bazel 6 support as they were used in j2objc-related code.

[erikkerber]

Kept the macro name, dropped _dummy_lib and the cfg params, and modified the note to delete when Bazel 6 is dropped.

[mattrobmattrob]

_dummy_lib was used as part of some function of using the j2objc functionality?

[erikkerber]

It was part of the attributes returned in the macro so I assume so. CI passes with it deleted, and that's all the comfort I can provide ¯\_(ツ)_/¯

[luispadron]

I'm cool with merging this, in general no idea why we have / need the j2objc stuff in open source.

@brentleyjones thoughts?

[mattrobmattrob]

Fine to merge as well. We can revert or handle a different way if problems come up or someone with more knowledge chimes in.