On sparc64+ext4, suppress test failures from known WAL read failure.

Buildfarm members kittiwake, tadarida and snapper began to fail
frequently when commits 3cd9c3b921 and
f47ed79cc8 added tests of concurrency, but
the problem was reachable before those commits.  Back-patch to v10 (all
supported versions).

Discussion: https://postgr.es/m/20220116210241.GC756210@rfd.leadboat.com

contrib/amcheck/t/003_cic_2pc.pl

@@ -11,6 +11,8 @@ use TestLib;
 
 use Test::More tests => 5;
 
+local $TODO = 'filesystem bug' if TestLib::has_wal_read_bug;
+
 my ($node, $result);
 
 #

src/test/perl/TestLib.pm

@@ -315,6 +315,29 @@ sub perl2host
 
 =pod
 
+=item has_wal_read_bug()
+
+Returns true if $tmp_check is subject to a sparc64+ext4 bug that causes WAL
+readers to see zeros if another process simultaneously wrote the same offsets.
+Consult this in tests that fail frequently on affected configurations.  The
+bug has made streaming standbys fail to advance, reporting corrupt WAL.  It
+has made COMMIT PREPARED fail with "could not read two-phase state from WAL".
+Non-WAL PostgreSQL reads haven't been affected, likely because those readers
+and writers have buffering systems in common.  See
+https://postgr.es/m/20220116210241.GC756210@rfd.leadboat.com for details.
+
+=cut
+
+sub has_wal_read_bug
+{
+	return
+	     $Config{osname} eq 'linux'
+	  && $Config{archname} =~ /^sparc/
+	  && !run_log([ qw(df -x ext4), $tmp_check ], '>', '/dev/null', '2>&1');
+}
+
+=pod
+
 =item system_log(@cmd)
 
 Run (via C<system()>) the command passed as argument; the return