pgsql: Fix pg_waldump/t/001_basic.pl with BSD tar on ZFS.

Fix pg_waldump/t/001_basic.pl with BSD tar on ZFS.

The new test fails with an error about a missing WAL file on that
stack, because it is archived in GNU tar's --sparse --format=posix
format. BSD tar uses that format by default, unlike GNU tar itself, and
ZFS triggers it by implicitly creating sparse files when it sees a lot
of zeroes.

The problem will surely also affect real users of the new tar support in
pg_waldump (commit b15c1513) and pg_verifybackup (commit b3cf461b3) on
such systems. Ideas under discussion, but for now the test is made to
pass by disabling sparse file detection in BSD tar.

Diagnosed-by: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
Reviewed-by: Andrew Dunstan <andrew(at)dunslane(dot)net>
Discussion: https://postgr.es/m/1624716.1774736283%40sss.pgh.pa.us

Branch
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master

Details
-------
https://git.postgresql.org/pg/commitdiff/852de579a6eea3bebf719530ea2d2c232573b845

Modified Files
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src/bin/pg_waldump/t/001_basic.pl | 11 ++++++++++-
1 file changed, 10 insertions(+), 1 deletion(-)