[Bug bootstrap/69464] [6 Regression]: bootstrap failure on CentOS 5.11: error: ‘swap’ is not a member of ‘std’

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69464

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> ---
It's in <utility> now, so better to include both to be portable.