https://sourceware.org/legacy-ml/cygwin/2010-01/msg00998.html
Jeff Jones - Re: flex package requires m4
jeff jonesflex packagerequires
https://docs.cloud.google.com/dataflow/docs/guides/templates/configuring-flex-templates?authuser=2
Use Flex Templates to package a Dataflow pipeline for deployment | Google Cloud Documentation
Package Apache Beam pipelines into Dataflow Flex Templates.