[native_toolchain_c] Fix treeshaking on mac

[mosuem]

By creating a list of symbols to be exported.

Also needs to be tested with ICU4X, but manually setting this seems to do the trick to solve dart-lang/i18n#989

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[github-actions]

Package publishing

Package	Version	Status	Publish tag (post-merge)
package:code_assets	0.19.4	already published at pub.dev
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package:hooks	0.19.5	already published at pub.dev
package:hooks_runner	0.21.0	already published at pub.dev
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package:native_toolchain_c	0.17.0	ready to publish	native_toolchain_c-v0.17.0
package:objective_c	8.1.0-wip	WIP (no publish necessary)
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[github-actions]

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Breaking changes ⚠️

Package	Change	Current Version	New Version	Needed Version	Looking good?
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native_toolchain_c	Breaking	0.16.8	0.17.0	0.17.0	✔️

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API leaks ✔️

The following packages contain symbols visible in the public API, but not exported by the library. Export these symbols or remove them from your publicly visible API.

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pkgs/jni/lib/src/third_party/generated_bindings.dart
pkgs/native_doc_dartifier/lib/native_doc_dartifier.dart
pkgs/native_doc_dartifier/lib/src/native_doc_dartifier_base.dart
pkgs/objective_c/lib/src/ns_input_stream.dart

[coveralls]

coverage: 87.096% (-3.4%) from 90.52%
when pulling 1b27f49 on fixTreeshakeMac
into 3481346 on main.

[dcharkes]

Probably needs a test of some sort

We have tests for binary sizes: pkgs/native_toolchain_c/test/clinker/treeshake_helper.dart Shouldn't pkgs/native_toolchain_c/test/clinker/treeshake_test.dart and pkgs/native_toolchain_c/test/clinker/treeshake_cross_test.dart already invoke those? Why aren't those tests failing before this PR?

[goderbauer]

This will need some sort of a test to verify that a symbol that previously wasn't treeshaken on macos is now removed.

[goderbauer]

We have tests for binary sizes: pkgs/native_toolchain_c/test/clinker/treeshake_helper.dart Shouldn't pkgs/native_toolchain_c/test/clinker/treeshake_test.dart and pkgs/native_toolchain_c/test/clinker/treeshake_cross_test.dart already invoke those?

Yes, those are getting invoked.

Why aren't those tests failing before this PR?

It seems like prior to this PR some symbols were already treeshaken. The existing tests are confirming that. But apparently it doesn't treeshake some other symbols marked as global. We'll need a specific new test for those cases.

[mosuem]

Probably needs a test of some sort - I am open for ideas.

I agree on the calls for a test ;) I'll figure out how to build one.

[dcharkes]

Probably needs a test of some sort - I am open for ideas.

I agree on the calls for a test ;) I'll figure out how to build one.

Are the global symbols visible with dlsym? If yes, we could do DynamicLibrary.open().providesSymbol https://api.flutter.dev/flutter/dart-ffi/DynamicLibrary/providesSymbol.html

Otherwise, maybe add a global symbol that holds on to stuff? E.g. like a very very very long const char*? (In the order of megabytes.)