fix: build alpine binary inside an alpine container

This is needed as building a node10 alpine binary on a linux platform generates a bad binary which segfaults. Reason is unclear, this is a workaround.

.releaserc

@@ -2,9 +2,14 @@
   "prepare": [
     "@semantic-release/npm",
     {
-      "//": "build the alpine, macos, linux and windows binaries",
+      "//": "build the alpine binaries inside an alpine container",
       "path": "@semantic-release/exec",
-      "cmd": "npm i -g pkg && pkg . -t node8-alpine-x64,node8-linux-x64,node8-macos-x64,node8-win-x64"
+      "cmd": "docker run --rm -i -v `pwd`:/snyk node:alpine /snyk/scripts/build_alpine_binary.sh"
+    },
+    {
+      "//": "build the macos, linux and windows binaries",
+      "path": "@semantic-release/exec",
+      "cmd": "npm i -g pkg && pkg . -t node8-linux-x64,node8-macos-x64,node8-win-x64"
     },
     {
       "//": "shasum all binaries",

scripts/build_alpine_binary.sh

@@ -0,0 +1,19 @@
+#!/bin/sh
+
+# echo commands for debug purposes
+set -x
+# bail out in case of a single command failure
+set -e
+
+# this script is expected to run inside a node:alpine docker container
+# with the path /snyk mounted with the project folder
+cd /snyk
+npm install # install deps in case they are missing
+npm run prepare # explicit, as running as root would skip scripts
+
+# build the binary
+npm i -g pkg
+pkg . -t node10-alpine-x64 -o snyk-alpine
+
+# test it for validity
+./snyk-alpine -v