add build script

.gitignore

@@ -1 +1,5 @@
 scratch
+.DS_Store
+cmd/pbin/build.tgz
+cmd/pbin/build
+cmd/pbin/build/**

cmd/pbin/build.sh

@@ -0,0 +1,58 @@
+#!/usr/bin/env bash
+
+set -e
+
+DOCKERFILE="$(cat << EOF
+FROM golang:latest as build
+SHELL ["/bin/bash", "-c"]
+WORKDIR /build
+ADD . /build
+RUN go mod download
+RUN cd cmd/pbin && \
+    GOOS=darwin \
+    GOARCH=amd64 \
+    go build \
+        -a \
+        -o /build/pbin-darwin \
+        .
+RUN cd cmd/pbin && \
+    GOOS=linux \
+    GOARCH=amd64 \
+    go build \
+        -a \
+        -o /build/pbin-linux \
+        .
+RUN cd cmd/pbin && \
+    GOOS=windows \
+    GOARCH=amd64 \
+    go build \
+        -a \
+        -o /build/pbin-windows \
+        .
+RUN tar -cvzf build.tgz \
+    pbin-linux \
+    pbin-darwin \
+    pbin-windows
+FROM golang:latest
+COPY --from=build /build/build.tgz /opt/
+CMD ["cat", "/opt/build.tgz"]
+EOF
+)"
+
+function build
+{
+    local SCRIPT_PATH="$(dirname "$(readlink -f "${BASH_SOURCE[0]}")")"
+    pushd "${SCRIPT_PATH}"
+    while [[ "${PWD}" != '/' && ! -f "go.mod" ]] ; do
+        cd ..
+    done
+    docker build \
+        -t build:tmp \
+        -f - \
+        . <<< "${DOCKERFILE}"
+    docker run --rm build:tmp > "${SCRIPT_PATH}/build.tgz"
+    popd
+}
+
+build
+