make creating directories simpler

Co-authored-by: Andrew Murray <3112309+radarhere@users.noreply.github.com>

osx_utils.sh

@@ -453,10 +453,8 @@ function macos_arm64_cross_build_setup {
     # Setup cross build for single arch arm_64 wheels
     export PLAT="arm64"
     export BUILD_PREFIX=/opt/arm64-builds
-    sudo mkdir -p $BUILD_PREFIX
+    sudo mkdir -p $BUILD_PREFIX/lib $BUILD_PREFIX/include
     sudo chown -R $USER $BUILD_PREFIX
-    mkdir -p $BUILD_PREFIX/lib
-    mkdir -p $BUILD_PREFIX/include
     update_env_for_build_prefix
     export _PYTHON_HOST_PLATFORM="macosx-11.0-arm64"
     export CFLAGS+=" -arch arm64"