cmake : add install() for impl libraries + fix apple builds (#23511)

* pi : update

* ci : fix ios build

* ci : fix andoroid

* ci : fix apple builds

* cmake : add install() for impl libraries

Add install(TARGETS <target> LIBRARY) for all -impl libraries that were
changed from STATIC to shared (controlled by BUILD_SHARED_LIBS) in
commit bb28c1fe2. Without this, cmake --install fails to copy the shared
libraries, causing runtime errors like:

  llama-server: error while loading shared libraries: libllama-server-impl.so

Ref: https://github.com/ggml-org/llama.cpp/issues/23494#issuecomment-4512912515

Assisted-by: llama.cpp:local pi

* ci : fix xcframework build

tools/server/CMakeLists.txt

@@ -44,6 +44,10 @@ target_include_directories(${TARGET} PUBLIC ${CMAKE_CURRENT_SOURCE_DIR})
 target_include_directories(${TARGET} PRIVATE ../mtmd ${CMAKE_SOURCE_DIR})
 target_link_libraries(${TARGET} PUBLIC server-context llama-ui cpp-httplib ${CMAKE_THREAD_LIBS_INIT})
 
+if(LLAMA_TOOLS_INSTALL)
+    install(TARGETS ${TARGET} LIBRARY)
+endif()
+
 # llama-server executable
 
 set(TARGET llama-server)