Switch xcode support to Makefile-based approach

xcode/Makefile

@@ -0,0 +1,44 @@
+clean:
+	rm -rf ./cmutton*
+
+ios-hw:
+	CGO_ENABLED=1 \
+	GOOS=darwin \
+	GOARCH=arm64 \
+	SDK=iphoneos \
+	CC=$(PWD)/clangwrap.sh \
+	CGO_CFLAGS="-fembed-bitcode" \
+	go build -buildmode=c-archive -tags ios -o ./cmutton-ios-hw.a ..
+
+ios-sim:
+	CGO_ENABLED=1 \
+	GOOS=darwin \
+	GOARCH=arm64 \
+	SDK=iphonesimulator \
+	CC=$(PWD)/clangwrap.sh \
+	go build -buildmode=c-archive -tags ios -o ./cmutton-ios-sim.a ..
+
+macos:
+	CGO_ENABLED=1 \
+	GOOS=darwin \
+	GOARCH=arm64 \
+	SDK=macosx \
+	go build -buildmode=c-archive -o ./cmutton-macos-arm64.a ..
+
+ios: ios-hw ios-sim
+	xcodebuild -create-xcframework \
+	-library ./cmutton-ios-hw.a \
+	-headers ./cmutton-ios-hw.h \
+	-library ./cmutton-ios-sim.a \
+	-headers ./cmutton-ios-sim.h \
+	-output ./cmutton.xcframework
+
+apple: ios-hw ios-sim macos
+	xcodebuild -create-xcframework \
+	-library ./cmutton-ios-hw.a \
+	-headers ./cmutton-ios-hw.h \
+	-library ./cmutton-ios-sim.a \
+	-headers ./cmutton-ios-sim.h \
+	-library ./cmutton-macos-arm64.a \
+	-headers ./cmutton-macos-arm64.h \
+	-output ./cmutton.xcframework