[BigSur] CMake build cannot link to cached dylib

• Component: CMake
• Status: NEW ---

[lecris]

I am trying to port webkit-gtk to homebrew, but I am running into a roadblock with one of the packages used (probably `WTF`'s link to `ICU`). The exact error is:
```
make[3]: *** No rule to make target `/usr/lib/libicucore.dylib', needed by `bin/LLIntSettingsExtractor'.  Stop.
make[2]: *** [Source/JavaScriptCore/CMakeFiles/LLIntSettingsExtractor.dir/all] Error 2
```

In BigSur, Mac has switched to using cached dylib so there is no `/usr/lib/libicucore.dylib`, instead `.tbd` is used. From what I've read with CMake >3.19 these libraries are picked up correctly, however this doesn't seem to be the case in this project. A new target `/usr/lib/libicucore.dylib` is generated after the config stage, but I am not able to track down to why and how it is generated. Could anyone help point me to the appropriate section, and if possible to a resolution to this issue?

[lecris]

I have since resolved this issue by adding `find_package(ICU COMPONENTS data uc i18n REQUIRED)`, however a bunch more errors have appeared due to the CMAKE project not accounting for a`GTK` build on `MacOS`. Some are trivial fixes like the `namespace` not being added or a `const` function pointing to a non-static member. I am able to solve some of these issues, but there are a few issues I would like to ask for some help with. Currently one unresolved issue is:
```
../Source/WebKit/Shared/SandboxExtension.h:120:74: error: use of undeclared identifier 'audit_token_t'
```

[Radar WebKit Bug Importer]

<rdar://problem/76044123>