Do not show error message if errno = 0 for flush fail on STDOUT

Somehow (on HP-UX Itanium) the flush fails, but errno is still 0
The lib/warnings.t test then shows

EXPECTED:
Filehandle STDOUT opened only for output at - line 3.
GOT:
Filehandle STDOUT opened only for output at - line 3.
Unable to flush stdout: Error 0

This change suppresses that last line if errno is (still) 0

1 files changed, 3 insertions, 2 deletions

diff --git a/perl.c b/perl.c
index 6618535741..1ceed1cd85 100644
--- a/perl.c
+++ b/perl.c
@@ -621,8 +621,9 @@ perl_destruct(pTHXx)
         PerlIO *stdo = PerlIO_stdout();
         if (*stdo && PerlIO_flush(stdo)) {
             PerlIO_restore_errno(stdo);
-            PerlIO_printf(PerlIO_stderr(), "Unable to flush stdout: %s",
-                          Strerror(errno));
+            if (errno)
+                PerlIO_printf(PerlIO_stderr(), "Unable to flush stdout: %s",
+                    Strerror(errno));
             if (!STATUS_UNIX)
                 STATUS_ALL_FAILURE;
         }