Bump gcc requirement to gcc >= 7 as C++17 is mandatory since https://github.com/MusicPlayerDaemon/ncmpc/commit/85f136dd6b6a8d044b19cbef818ee360292cc06e Signed-off-by: Fabrice Fontaine <fontaine.fabrice@gmail.com> Signed-off-by: Peter Korsgaard <peter@korsgaard.com>