Add command to build_static

Uploading the object file and linking it on the server wasn't working. So I'm now using a statically linked binary.

I followed the instructions here: https://crystal-lang.org/reference/1.10/guides/static_linking.html#linux

script/build_static

@@ -0,0 +1,20 @@
+#!/usr/bin/env bash
+
+# Exit if any subcommand fails
+set -e
+set -o pipefail
+
+todays_date=$(date "+%Y-%m-%d")
+if ! git show HEAD:src/version.cr | rg -q $todays_date; then
+  echo "Date in committed src/version.cr is not today's date ($todays_date)"
+  echo "Make sure that the file is both up to date and commited to git."
+  echo
+  echo "## src/version.cr"
+  git show HEAD:src/version.cr
+  # exit 1
+fi
+
+# Via: https://crystal-lang.org/reference/1.10/guides/static_linking.html#linux
+
+~/.docker/bin/docker run --rm -it -v $(pwd):/workspace -w /workspace crystallang/crystal:latest-alpine \
+  crystal build src/start_server.cr -o ubuntu_server --static --release