enhancement: better clarification of search side effects

[Radisson97]

Hello List,
today i had a strange problem with a long used makefile (GNU Make 4.3).
It found a file called "all.sh" and did a "cat <all.sh >all". It took me a while
to figure out was was going on.

I use makefile for a long time but that effect happend the first time to me.
It would be helpful to improve the documentation that people will be aware
that this can happen. The phony section has some hints this way, maybe this
is a good example to show what happens if you do not use phony.

note: i am not a list member please reply directly if needed.

CU