bin/55360: usr.bin/make/t_make:include_sub, include_subsub test cases fail since inception

[gson%gson.org@localhost (Andreas Gustafsson)]

>Number:         55360
>Category:       bin
>Synopsis:       usr.bin/make/t_make:include_sub, include_subsub test cases fail since inception
>Confidential:   no
>Severity:       serious
>Priority:       medium
>Responsible:    bin-bug-people
>State:          open
>Class:          sw-bug
>Submitter-Id:   net
>Arrival-Date:   Mon Jun 08 12:20:00 +0000 2020
>Originator:     Andreas Gustafsson
>Release:        NetBSD-current, source date >= 2020.05.17.12.36.26
>Organization:
>Environment:
System: NetBSD
Architecture: x86_64
Machine: amd64
>Description:

The include_sub and include_subsub test cases of the usr.bin/make/t_make test
program have been failing ever since they were added in this commit:

  2020.05.17.12.36.26 rillig src/distrib/sets/lists/tests/mi 1.841
  2020.05.17.12.36.26 rillig src/usr.bin/make/unit-tests/Makefile 1.58
  2020.05.17.12.36.26 rillig src/usr.bin/make/unit-tests/include-main.exp 1.1
  2020.05.17.12.36.26 rillig src/usr.bin/make/unit-tests/include-main.mk 1.1
  2020.05.17.12.36.26 rillig src/usr.bin/make/unit-tests/include-sub.mk 1.1
  2020.05.17.12.36.26 rillig src/usr.bin/make/unit-tests/include-subsub.mk 1.1

If they are failing on purpose to demonstrate a known bug, they should
be marked as "expected failures" with a reference to a PR.

>How-To-Repeat:

Run the ATF tests.

>Fix: