Fix iOS IPA CI failure: generate PPC recompiled sources before iOS configure

[Copilot]

The "Configure iOS build with CMake" step failed with CMake Error ... Cannot find source file: UnleashedRecompLib/ppc/ppc_config.h because the iOS build path never generated its required sources.

Root cause

• UnleashedRecompLib/CMakeLists.txt sets UNLEASHED_RECOMP_USE_PREGENERATED_RECOMP=ON for iOS, skipping the XenonRecomp/XenosRecomp custom commands that produce ppc/* and shader/shader_cache.cpp.
• These files are gitignored (ppc_*) and expected to be pre-generated by a prior host build.
• The workflow's host "Generate SPIR-V headers for iOS" step only built UnleashedRecompShaders and UnleashedRecompResources, never triggering PPC source generation — so the iOS configure step found nothing to compile against.

Changes

• UnleashedRecompLib/CMakeLists.txt: added an UnleashedRecompPPC custom target that depends only on the generated PPC/shader source files (mirrors the existing UnleashedRecompShaders/UnleashedRecompResources targets), so the sources can be generated without compiling the full library.
• .github/workflows/build-ios-ipa.yml: the host macOS "Generate SPIR-V headers for iOS" step now also builds UnleashedRecompPPC, ensuring pregenerated sources exist on disk before the iOS CMake configure runs.

# UnleashedRecompLib/CMakeLists.txt
add_custom_target(UnleashedRecompPPC DEPENDS
    ${UNLEASHED_RECOMP_PPC_RECOMPILED_SOURCES}
    "${CMAKE_CURRENT_SOURCE_DIR}/shader/shader_cache.cpp"
)

# .github/workflows/build-ios-ipa.yml
cmake --build . --target UnleashedRecompShaders UnleashedRecompResources UnleashedRecompPPC