auto-phony.sh

#/bin/sh

# Automatically generate .PHONY for Makefile

MAKEFILE=$1

cat $MAKEFILE | \
grep -E  '^[a-zA-Z\-_0-9.]+:' | \
grep -Ev '^\.PHONY:' | \
grep -Ev '#.*NO_PHONY' | \
cut -d ':' -f 1 | tr '\n' ' ' | sed -e 's/ $/\n/g'

You don't want to add task to .PHONY?

Add # NO_PHONY in the same line of the task.

task: foo bar # NO_PHONY