Switch xcode support to Makefile-based approach

xcode/clangwrap.sh

@@ -0,0 +1,20 @@
+#!/bin/sh
+
+MIN_VERSION=26.0
+
+SDK_PATH=`xcrun --sdk $SDK --show-sdk-path`
+CLANG=`xcrun --sdk $SDK --find clang`
+
+if [ "$SDK" = "iphoneos" ]; then
+  export TARGET="-target $CARCH-apple-ios$MIN_VERSION"
+elif [ "$SDK" = "iphonesimulator" ]; then
+  export TARGET="-target $CARCH-apple-ios$MIN_VERSION-simulator"
+fi
+
+if [ "$GOARCH" == "amd64" ]; then
+    CARCH="x86_64"
+elif [ "$GOARCH" == "arm64" ]; then
+    CARCH="arm64"
+fi
+
+exec $CLANG -arch $CARCH $TARGET -isysroot $SDK_PATH -mios-version-min=$MIN_VERSION "$@"