Add build.sh to build dropbearmulti inside a docker

Dockerfile

@@ -0,0 +1,14 @@
+FROM alpine:3.17.1 AS builder
+
+RUN apk add --no-cache alpine-sdk
+RUN apk add --no-cache \
+    musl-dev \
+    zlib-dev \
+    tar \
+    bzip2 \
+    bash
+
+RUN mkdir -p /root/dropbear/
+WORKDIR /root/dropbear/
+
+ENTRYPOINT ["bash"]

build.sh

@@ -0,0 +1,7 @@
+#!/bin/bash
+
+docker build -t dropbearbuild -f Dockerfile .
+
+docker run --rm -t -v $(pwd):/root/dropbear dropbearbuild -c "./configure --disable-utmp --disable-wtmp --disable-lastlog --disable-zlib --disable-syslog --enable-static --disable-harden && make clean && make -j4 MULTI=1 PROGRAMS=\"dropbear dropbearconvert dropbearkey\" && mv dropbearmulti dropbearmulti_ && make clean && mv dropbearmulti_ dropbearmulti"
+
+docker image rm dropbearbuild