[brentleyjones]

Add a per-target generate_linkmap attribute to Apple binary rules while preserving --objc_generate_linkmap as a global override.

Validation:

• Regenerated documentation with bazel run //doc:update; all 15 documentation checks pass.
• All 11 targeted linkmap analysis tests pass, covering the per-target attribute, linker arguments, output groups, the global flag, and XCFrameworks.
• Buildifier formatting and lint checks pass.