Link backend to prtable libs (#12268)

### Summary
1. Link portable OPs and kernels
2. Remove unused cmake checks

Author: neuropilot-captain

backends/mediatek/CMakeLists.txt

@@ -27,6 +27,8 @@ target_compile_options(neuron_backend PRIVATE "-frtti" "-fexceptions")
 target_link_libraries(neuron_backend
     PRIVATE
     executorch_core
+    portable_ops_lib
+    portable_kernels
     android
     log
 )

backends/mediatek/scripts/mtk_build.sh

@@ -6,12 +6,6 @@ set -e
 # Define the directory where CMakeLists.txt is located
 SOURCE_DIR=$(realpath "$(dirname "$0")/../../..")
 
-# Check if buck2 exists
-BUCK_PATH=${BUCK2:-buck2}
-if [ -z "$BUCK2" ]; then
-    echo "Info: BUCK2 environment variable is not set." >&2
-fi
-
 # Check if the ANDROID_NDK environment variable is set
 if [ -z "$ANDROID_NDK" ]; then
     echo "Error: ANDROID_NDK environment variable is not set." >&2

examples/mediatek/mtk_build_examples.sh

@@ -7,12 +7,6 @@ set -e
 EXECUTORCH_ROOT=$(realpath "$(dirname "$0")/../..")
 echo EXECUTORCH_ROOT=${EXECUTORCH_ROOT}
 
-# Check if buck2 exists
-BUCK_PATH=${BUCK2:-buck2}
-if [ -z "$BUCK2" ]; then
-    echo "Info: BUCK2 environment variable is not set." >&2
-fi
-
 # Check if the ANDROID_NDK environment variable is set
 if [ -z "$ANDROID_NDK" ]; then
     echo "Error: ANDROID_NDK environment variable is not set." >&2
@@ -30,7 +24,6 @@ main() {
     # Configure the project with CMake
     # Note: Add any additional configuration options you need here
     cmake -DCMAKE_INSTALL_PREFIX="${build_dir}" \
-          -DBUCK2="$BUCK_PATH" \
           -DCMAKE_TOOLCHAIN_FILE="$ANDROID_NDK/build/cmake/android.toolchain.cmake" \
           -DANDROID_ABI=arm64-v8a \
           -DANDROID_NATIVE_API_LEVEL=26 \