ci: support darwin-arm64 NDK host in mieru.sh

Add a darwin-arm64 fallback for the NDK LLVM toolchain so local Mieru builds
work natively on Apple Silicon Macs (newer NDKs ship darwin-arm64).

Author: hawkff

buildScript/lib/mieru.sh

@@ -20,10 +20,13 @@ fi
 MIERU_VERSION="${MIERU_VERSION:-v3.34.0}"
 
 DEPS="$ANDROID_NDK_HOME/toolchains/llvm/prebuilt/linux-x86_64/bin"
-# macOS NDK host dir is darwin-x86_64; fall back if linux path is absent.
+# macOS NDK host dirs are darwin-x86_64 / darwin-arm64; fall back if linux is absent.
 if [ ! -d "$DEPS" ]; then
   DEPS="$ANDROID_NDK_HOME/toolchains/llvm/prebuilt/darwin-x86_64/bin"
 fi
+if [ ! -d "$DEPS" ]; then
+  DEPS="$ANDROID_NDK_HOME/toolchains/llvm/prebuilt/darwin-arm64/bin"
+fi
 if [ ! -d "$DEPS" ]; then
   echo "Error: NDK LLVM toolchain not found under $ANDROID_NDK_HOME (unsupported host or NDK layout)." >&2
   exit 1