Build Android in one pass (#12323)

### Summary
Now trigger cmake once. 
Fixes #10120 

### Test plan
CI

Author: kirklandsign

CMakeLists.txt

@@ -732,4 +732,8 @@ if(EXECUTORCH_BUILD_VULKAN)
   add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/backends/vulkan)
 endif()
 
+if(EXECUTORCH_BUILD_ANDROID_JNI)
+  add_subdirectory(${CMAKE_CURRENT_SOURCE_DIR}/extension/android)
+endif()
+
 include(Test.cmake)

extension/android/CMakeLists.txt

@@ -61,7 +61,6 @@ set_target_properties(fbjni PROPERTIES
 )
 
 set(executorch_DIR ${CMAKE_CURRENT_BINARY_DIR}/../../lib/cmake/ExecuTorch)
-find_package(executorch CONFIG REQUIRED)
 target_link_options_shared_lib(executorch)
 
 add_library(executorch_jni SHARED jni/jni_layer.cpp jni/log.cpp jni/jni_layer_runtime.cpp)

scripts/build_android_library.sh

@@ -41,6 +41,7 @@ build_android_native_library() {
     -DBUILD_TESTING=OFF \
     -DEXECUTORCH_PAL_DEFAULT=android \
     -DEXECUTORCH_ENABLE_LOGGING=ON \
+    -DEXECUTORCH_BUILD_ANDROID_JNI=ON \
     -DEXECUTORCH_BUILD_DEVTOOLS=ON \
     -DEXECUTORCH_ENABLE_EVENT_TRACER="${EXECUTORCH_ANDROID_PROFILING:-OFF}" \
     -DEXECUTORCH_LOG_LEVEL=Info \
@@ -55,6 +56,7 @@ build_android_native_library() {
     -DEXECUTORCH_BUILD_KERNELS_OPTIMIZED=ON \
     -DEXECUTORCH_BUILD_KERNELS_QUANTIZED=ON \
     -DEXECUTORCH_BUILD_KERNELS_CUSTOM="${EXECUTORCH_BUILD_EXTENSION_LLM:-ON}" \
+    -DEXECUTORCH_BUILD_LLAMA_JNI="${EXECUTORCH_BUILD_EXTENSION_LLM:-ON}" \
     -DEXECUTORCH_BUILD_NEURON="${EXECUTORCH_BUILD_NEURON}" \
     -DNEURON_BUFFER_ALLOCATOR_LIB="${NEURON_BUFFER_ALLOCATOR_LIB}" \
     -DEXECUTORCH_BUILD_QNN="${EXECUTORCH_BUILD_QNN}" \
@@ -71,25 +73,6 @@ build_android_native_library() {
   fi
   cmake --build "${CMAKE_OUT}" -j "${CMAKE_JOBS}" --target install --config "${EXECUTORCH_CMAKE_BUILD_TYPE}"
 
-  cmake extension/android \
-    -DCMAKE_TOOLCHAIN_FILE=${ANDROID_NDK}/build/cmake/android.toolchain.cmake \
-    -DANDROID_ABI="${ANDROID_ABI}" \
-    -DANDROID_PLATFORM=android-26 \
-    -DBUILD_TESTING=OFF \
-    -DCMAKE_INSTALL_PREFIX="${CMAKE_OUT}" \
-    -DEXECUTORCH_ENABLE_LOGGING=ON \
-    -DEXECUTORCH_LOG_LEVEL=Info \
-    -DCMAKE_FIND_ROOT_PATH_MODE_PACKAGE=BOTH \
-    -DEXECUTORCH_ANDROID_PROFILING="${EXECUTORCH_ANDROID_PROFILING:-OFF}" \
-    -DNEURON_BUFFER_ALLOCATOR_LIB="$NEURON_BUFFER_ALLOCATOR_LIB" \
-    -DEXECUTORCH_BUILD_KERNELS_CUSTOM="${EXECUTORCH_BUILD_EXTENSION_LLM:-ON}" \
-    -DEXECUTORCH_BUILD_LLAMA_JNI="${EXECUTORCH_BUILD_EXTENSION_LLM:-ON}" \
-    -DSUPPORT_REGEX_LOOKAHEAD=ON \
-    -DCMAKE_BUILD_TYPE="${EXECUTORCH_CMAKE_BUILD_TYPE}" \
-    -B"${CMAKE_OUT}"/extension/android
-
-  cmake --build "${CMAKE_OUT}"/extension/android -j "${CMAKE_JOBS}" --config "${EXECUTORCH_CMAKE_BUILD_TYPE}"
-
   # Copy artifacts to ABI specific directory
   local SO_STAGE_DIR="cmake-out-android-so/${ANDROID_ABI}"
   mkdir -p ${SO_STAGE_DIR}