Revert "Check that we have a working tar before trying to use it"

This reverts commit f920f7e799c587228227ec94356c760e3f3d5f2b.

The patch in effect fixed a problem we didn't have and caused another
instead.

Backpatch to release 14 like original

Discussion: https://postgr.es/m/3655283.1638977975@sss.pgh.pa.us

src/bin/pg_basebackup/t/010_pg_basebackup.pl

@@ -267,9 +267,11 @@ is(scalar(@tblspc_tars), 1, 'one tablespace tar was created');
 SKIP:
 {
 	my $tar = $ENV{TAR};
+	# don't check for a working tar here, to accomodate various odd
+	# cases such as AIX. If tar doesn't work the init_from_backup below
+	# will fail.
 	skip "no tar program available", 1
-	  if (!defined $tar || $tar eq ''
-		  || system_log($tar, '--version') != 0);
+	  if (!defined $tar || $tar eq '');
 
 	my $node2 = get_new_node('replica');