Avoid clobbering errno, per comment from Tom.

src/port/exec.c

@@ -357,8 +357,8 @@ pipe_read_line(char *cmd, char *line, int maxsize)
 
 	if (fgets(line, maxsize, pgver) == NULL)
 	{
-		pclose(pgver);		/* no error checking */
 		perror("fgets failure");
+		pclose(pgver);		/* no error checking */
 		return NULL;
 	}