[tlbuild] Input stack overflow problems in test suite on NetBSD

[Marc Baudoin]

The following problem appeared in the test suite following one of
the recent commits:

% egrep 'overflow|FAIL' Work/texk/web2c/test-suite.log
# XFAIL: 0
# FAIL:  2
FAIL: pmpostdir/pmpsamp
Preloading the plain mem file, version 1.005)input stack overflow
FAIL pmpostdir/pmpsamp.test (exit status: 1)
FAIL: pmpostdir/upmpsamp
Preloading the plain mem file, version 1.005)input stack overflow
FAIL pmpostdir/upmpsamp.test (exit status: 1)

It might be related to:

2021-05-09  Luigi Scarso  <luigi.scarso at gmail.com>
        * Impose mp->stack_size < 1001 in @d push_input to avoid stack overflow
          due infinite recursion of macro expansion (thanks to A. Kakuto).