Set ac_cv_strftime_c99_support=yes for cache

Author: zanieb

configure

@@ -6684,9 +6684,9 @@ int main(void)
   return 1;
 }
 ]])],
-[],
+[ac_cv_strftime_c99_support=yes],
 [AC_MSG_ERROR([Python requires C99-compatible strftime specifiers])],
-[]))])
+[])])
 
 dnl check for ncursesw/ncurses and panelw/panel
 dnl NOTE: old curses is not detected.