[louwers]

Fixes #2241

docc_archive only supported Swift. This adds Objective-C support by extracting symbol graphs from the public headers (hdrs) of objc_library targets with clang -extract-api, the same tool Xcode uses for Objective-C DocC.

• The extraction uses the target's propagated compilation context (includes, defines, framework search paths). The -target triple comes from the C++ toolchain and the SDK from the target platform. -fmodules is passed when enable_modules is set or -fmodules is in copts.
• A DocC archive documents a single module. Unlike Swift symbol graphs, which are still transitive as before, Objective-C symbol graphs of transitive dependencies are not included: including them produces MultipleRootPages warnings and unresolved links from the .docc bundle. Targets that don't define a module themselves forward the Objective-C symbol graphs of their direct deps: bundling rules like ios_framework, or objc_library targets without public headers. The latter can be used to attach a .docc bundle to an existing library without it ending up as a resource in the app bundle.
• emit_extension_block_symbols = "1" also adds --emit-extension-symbol-graphs for Objective-C, which includes members of categories on types from other modules.
• New source_service and source_service_base_url attributes (mapping to docc convert --source-service / --source-service-base-url) link symbols to their source files. Symbol graphs reference files relative to the execution root, so the symbol graph collection step anchors those paths at a fixed checkout path that is passed as --checkout-path. That keeps outputs deterministic. Generated (bazel-out/) and external/ files are not linked.

Tested with new Starlark tests covering:

• an Objective-C library
• an Objective-C library with a .docc bundle
• an ios_framework with Objective-C deps
• a header-less objc_library wrapper with a .docc bundle
• source_service

I also used it to replace the bespoke DocC script in MapLibre Native (maplibre/maplibre-native#4738). The output matches the script's, with source links added for headers the script couldn't link.

🤖 Generated with Claude Code

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