Fix the error of missing curl in Dockerfile

Dockerfile

@@ -2,7 +2,7 @@
 # STEP 1 build executable binary
 ############################
 FROM golang:alpine AS builder
-RUN apk update && apk add --no-cache git bash wget
+RUN apk update && apk add --no-cache git bash wget curl
 WORKDIR /go/src/v2ray.com/core
 RUN git clone --progress https://github.com/v2fly/v2ray-core.git . && \
     bash ./release/user-package.sh nosource noconf codename=$(git describe --tags) buildname=docker-fly abpathtgz=/tmp/v2ray.tgz