misc/ios: pick clang arch based on GOARCH

Change-Id: Ia49ab729747acb07bf392d90aea9e752471e152e
Reviewed-on: https://go-review.googlesource.com/8789Reviewed-by: Minux Ma <minux@golang.org>

misc/ios/clangwrap.sh

@@ -7,4 +7,14 @@ SDK_PATH=`xcrun --sdk $SDK --show-sdk-path`
 export IPHONEOS_DEPLOYMENT_TARGET=5.1
 # cmd/cgo doesn't support llvm-gcc-4.2, so we have to use clang.
 CLANG=`xcrun --sdk $SDK --find clang`
-exec $CLANG -arch armv7 -isysroot $SDK_PATH "$@"
+
+if [ "$GOARCH" == "arm" ]; then
+	CLANGARCH="armv7"
+elif [ "$GOARCH" == "arm64" ]; then
+	CLANGARCH="arm64"
+else
+	echo "unknown GOARCH=$GOARCH" >&2
+	exit 1
+fi
+
+exec $CLANG -arch $CLANGARCH -isysroot $SDK_PATH "$@"