add musl build target(like new version of openwrt)

Makefile

@@ -4,21 +4,27 @@ GOBUILD=$(GOCMD) build
 GOCLEAN=$(GOCMD) clean
 VERSION=$(shell git describe --tags)
 DEBUG_LDFLAGS=''
-RELEASE_LDFLAGS='-s -w -X main.version=$(VERSION)'
+RELEASE_LDFLAGS=-s -w -X main.version=$(VERSION)
 BUILD_TAGS?=socks
 BUILDDIR=$(shell pwd)/build
 CMDDIR=$(shell pwd)/cmd/tun2socks
 PROGRAM=tun2socks
 
-BUILD_CMD="cd $(CMDDIR) && $(GOBUILD) -ldflags $(RELEASE_LDFLAGS) -o $(BUILDDIR)/$(PROGRAM) -v -tags '$(BUILD_TAGS)'"
-XBUILD_CMD="cd $(BUILDDIR) && $(XGOCMD) -ldflags $(RELEASE_LDFLAGS) -tags '$(BUILD_TAGS)' --targets=*/* $(CMDDIR)"
+BUILD_CMD="cd $(CMDDIR) && $(GOBUILD) -ldflags '$(RELEASE_LDFLAGS)' -o $(BUILDDIR)/$(PROGRAM) -v -tags '$(BUILD_TAGS)'"
+BUILD_MUSL_CMD="cd $(CMDDIR) && CC=musl-gcc $(GOBUILD) -ldflags '$(RELEASE_LDFLAGS) -linkmode external -extldflags \"-static\" ' -o $(BUILDDIR)/$(PROGRAM) -v -tags '$(BUILD_TAGS)'"
+XBUILD_CMD="cd $(BUILDDIR) && $(XGOCMD) -ldflags '$(RELEASE_LDFLAGS)' -tags '$(BUILD_TAGS)' --targets=*/* $(CMDDIR)"
 
 all: build
 
 build:
 	mkdir -p $(BUILDDIR)
 	eval $(BUILD_CMD)
 
+build_musl:
+	mkdir -p $(BUILDDIR)
+	eval $(BUILD_CMD)
+
+
 xbuild:
 	mkdir -p $(BUILDDIR)
 	eval $(XBUILD_CMD)

README.md

@@ -20,3 +20,13 @@ The following projects are using go-tun2socks:
 
 - https://github.com/mellow-io/mellow
 - https://github.com/eycorsican/kitsunebi-android
+
+-------
+## build for musl
+This build target depends on musl-gcc which can find in system path  
+
+You can build for musl system by using this command  
+```bash
+make build_musl
+```
+