[MacOS] Small changes to libtorch naming

Intel x86 libtorch builds will have `x86_64` suffix and Apple Silicon ones will have `arm64` ones, but latest will point to Intel ones for now.

wheel/build_wheel.sh

@@ -99,10 +99,10 @@ mkdir -p "$whl_tmp_dir"
 
 if [[ -n "$CROSS_COMPILE_ARM64" || $(uname -m) == "arm64" ]]; then
     mac_version='macosx_11_0_arm64'
-    libtorch_arch='-arm64-'
+    libtorch_arch='arm64'
 else
     mac_version='macosx_10_9_x86_64'
-    libtorch_arch=''
+    libtorch_arch='x86_64'
 fi
 
 # Create a consistent wheel package name to rename the wheel to
@@ -266,7 +266,7 @@ else
         cp -r "$(pwd)/any_wheel/torch/lib/include" "$(pwd)/libtorch/"
     fi
     cp -r "$(pwd)/any_wheel/torch/share/cmake" "$(pwd)/libtorch/share/"
-    if [[ "${libtorch_arch}" != "-arm64-" ]]; then
+    if [[ "${libtorch_arch}" == "x86_64" ]]; then
       if [[ -x "$(pwd)/any_wheel/torch/.dylibs/libiomp5.dylib" ]]; then
           cp -r "$(pwd)/any_wheel/torch/.dylibs/libiomp5.dylib" "$(pwd)/libtorch/lib/"
       else
@@ -278,7 +278,12 @@ else
     echo $PYTORCH_BUILD_VERSION > libtorch/build-version
     echo "$(pushd $pytorch_rootdir && git rev-parse HEAD)" > libtorch/build-hash
 
-    zip -rq "$PYTORCH_FINAL_PACKAGE_DIR/libtorch-macos${libtorch_arch}-$PYTORCH_BUILD_VERSION.zip" libtorch
-    cp "$PYTORCH_FINAL_PACKAGE_DIR/libtorch-macos${libtorch_arch}-$PYTORCH_BUILD_VERSION.zip"  \
-       "$PYTORCH_FINAL_PACKAGE_DIR/libtorch-macos${libtorch_arch}-latest.zip"
+    zip -rq "$PYTORCH_FINAL_PACKAGE_DIR/libtorch-macos-${libtorch_arch}-$PYTORCH_BUILD_VERSION.zip" libtorch
+    cp "$PYTORCH_FINAL_PACKAGE_DIR/libtorch-macos-${libtorch_arch}-$PYTORCH_BUILD_VERSION.zip"  \
+       "$PYTORCH_FINAL_PACKAGE_DIR/libtorch-macos-${libtorch_arch}-latest.zip"
+    if [[ "${libtorch_arch}" == "x86_64" ]]; then
+      # For backward compatibility make unarched latest to point to x86_64
+      cp "$PYTORCH_FINAL_PACKAGE_DIR/libtorch-macos-${libtorch_arch}-$PYTORCH_BUILD_VERSION.zip"  \
+         "$PYTORCH_FINAL_PACKAGE_DIR/libtorch-macos-latest.zip"
+    fi
 fi