build : use umbrella Headers directory for XCFramework module map

[gmarzjr]

Overview

The XCFramework generated by build-xcframework.sh creates a module map that manually lists public headers.

That list can fall out of sync with the framework's Headers directory. The module map is currently missing ggml-opt.h, which is present in the framework headers. This can cause downstream Apple builds to fail with:

Include of non-modular header inside framework module 'llama'

Use the framework's Headers directory itself as the module map umbrella instead of maintaining a manual header list. This makes all public headers under the generated framework's Headers directory part of the llama module.

Additional information

The generated llama.xcframework contains a llama.framework bundle. Inside that framework, the public headers are copied into llama.framework/Headers, and llama.framework/Modules/module.modulemap tells Clang which of those headers belong to the importable llama module.

This issue shows up when a downstream Apple build imports the generated framework as a module. In that case, Clang expects headers included by llama.h to also be declared by the framework's module map. Since ggml-opt.h is present in llama.framework/Headers but missing from module.modulemap, the import can fail as a non-modular include.

Projects that build llama.cpp directly from source, or consume the headers without importing the generated framework module, may not hit this error.

Verification:

• Built the XCFramework before this change and consumed it from a downstream iOS build.
• The build failed because llama.h includes ggml-opt.h, but ggml-opt.h was not listed in the generated module map.
• Rebuilt the XCFramework after this change.
• The same build succeeded.

Requirements

• I have read and agree with the contributing guidelines
• AI usage disclosure: Yes - I wrote and reviewed the code change. AI was used to analyze before/after build logs and review commit/PR wording.