These tests seem to trigger failures in the entire CI job (not just the
test) on AIX. Skip them to see if that helps alleviate spurious failures
in node-test-commit-aix (and the upstream PR and commit test jobs).

See:
- nodejs/build#1820 (comment)
- nodejs/build#1847 (comment)

PR-URL: nodejs#28469
Backport-PR-URL: nodejs#29599
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Daniel Bevenius <daniel.bevenius@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

Add SKIP status for more tests in stringbytes-external-exceed-max that
are failing on AIX.

PR-URL: nodejs#28516
Backport-PR-URL: nodejs#29599
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

Some pty tests persistently hung on the AIX CI buildbots. Fix that by
adding a helper script that properly sets up the pty before spawning
the script under test.

On investigation I discovered that the test runner hung when it tried
to close the slave pty's file descriptor, probably due to a bug in
AIX's pty implementation. I could reproduce it with a short C program.
The test runner also leaked file descriptors to the child process.

I couldn't convince python's `subprocess.Popen()` to do what I wanted
it to do so I opted to move the logic to a helper script that can do
fork/setsid/etc. without having to worry about stomping on state in
tools/test.py.

In the process I also uncovered some bugs in the pty module of the
python distro that ships with macOS 10.14, leading me to reimplement
a sizable chunk of the functionality of that module.

And last but not least, of course there are differences between ptys
on different platforms and the helper script has to paper over that.
Of course.

Really, this commit took me longer to put together than I care to admit.

Caveat emptor: this commit takes the hacky ^D feeding to the slave out
of tools/test.py and puts it in the *.in input files. You can also feed
other control characters to tests, like ^C or ^Z, simply by inserting
them into the corresponding input file. I think that's nice.

Fixes: nodejs/build#1820
Fixes: nodejs#28489

PR-URL: nodejs#28600
Backport-PR-URL: nodejs#29599
Reviewed-By: Richard Lau <riclau@uk.ibm.com>
Reviewed-By: Sam Roberts <vieuxtech@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

Assumption that if memory can be malloc()ed it can be used is not true
on AIX. Later access of the allocated pages can trigger SIGKILL if there
are insufficient VM pages.

Use psdanger() to better estimate available memory.

Fixes: nodejs/build#1849

More info:
- https://www.ibm.com/support/knowledgecenter/en/ssw_aix_71/generalprogramming/sys_mem_alloc.html
- https://www.ibm.com/support/knowledgecenter/en/ssw_aix_71/p_bostechref/psdanger.html

Related to:
- nodejs/build#1820 (comment)
- nodejs#28469
- nodejs#28516

PR-URL: nodejs#28857
Backport-PR-URL: nodejs#29599
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>
Reviewed-By: Beth Griggs <Bethany.Griggs@uk.ibm.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>

One skipped test remains, it creates very large Buffer objects,
triggering the AIX OOM to kill node and its parent processes.

See: nodejs/build#1849 (comment)

PR-URL: nodejs#29054
Backport-PR-URL: nodejs#29599
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Richard Lau <riclau@uk.ibm.com>