#!/usr/bin/env bash
set -euo pipefail
unset MAKEFLAGS MFLAGS GNUMAKEFLAGS
make_bin=$(command -v gmake || command -v make)
m() { "$make_bin" --no-print-directory -rR "$@"; }
work_dir=$(mktemp -d)
if [ "${KEEP_WORK:-0}" = 1 ]; then
  trap 'printf "Artifacts: %s\n" "$work_dir"' EXIT
else
  trap 'rm -rf -- "$work_dir"' EXIT
fi
cd "$work_dir"
export TMPDIR="$work_dir"
cat > Makefile <<'MAKEFILE'
.PHONY: all
all: a.txt b.txt
a.txt b.txt:
	@printf "%s\n" "$@"
	@printf "ready\n" > $@
MAKEFILE
m -s all
printf "again\n"
m -s all