[PATCH] Use automake (v5)

[Jon Turney]

On 20/04/2021 21:13, Jon Turney wrote:
> For ease of reviewing, this patch doesn't contain changes to generated
> files which would be made by running ./autogen.sh.

Sorry about getting distracted from this.  To summarize what I believe 
were the outstanding issues with v3 [1]:

[1] https://cygwin.com/pipermail/cygwin-patches/2020q4/010827.html

* 'INCLUDES' is the old name for 'AM_CPPFLAGS' warning from autogen.sh

I plan to clean this up in a future patch

* 'ps$(EXEEXT)' previously defined' warning from autogen.sh

It seems to be a shortcoming of automake that there's no way to suppress 
just that warning.

One possible solution is build ps.exe with a different name and rename 
it while installing, but I think that is counter-productive (in the 
sense that it trades this warning for making the build more complex to 
understand)

* some object files are in a unexpected places in the build file 
hierarchy (compared to naive expectations and/or the non-automake build)

I'm not sure if this is merely an aesthetic issue, or if there are 
problems this causes.