build: use nomad-builder docker image to build Nomad (#25626)

This introduces a docker image based off of ubuntu:bionic that can be used to
compile Nomad binary against glibc 2.27.

The image cannot build JS assets, which must be created before we compile the
Go binary.

.github/nomad-builder/Dockerfile

@@ -0,0 +1,28 @@
+# Copyright (c) HashiCorp, Inc.
+# SPDX-License-Identifier: BUSL-1.1
+
+FROM ubuntu:bionic
+
+ENV DEBIAN_FRONTEND=noninteractive
+
+ARG GO_VERSION
+
+RUN apt-get update && apt-get install -y --no-install-recommends \
+ bash \
+ build-essential \
+ ca-certificates \
+ crossbuild-essential-arm64 \
+ curl \
+ gcc-aarch64-linux-gnu \
+ git \
+ xz-utils \
+ zip
+
+# Get Go and get Going ;)
+RUN curl -L https://go.dev/dl/go${GO_VERSION}.linux-amd64.tar.gz | tar -C /opt -zxv
+
+ENV PATH="/root/go/bin:/opt/go/bin:$PATH"
+
+RUN git config --global --add safe.directory /build
+
+WORKDIR /build