* g10/gpg.c (oRequirePQCEncryption): New.
(opts): Add option.
(main): Set option.
* g10/mainproc.c (print_pkenc_list): Print a warning.
* g10/options.h (flags): Add flag require_pqc_encryption.
* g10/getkey.c (finish_lookup): Skip non-pqc keys if the option is
set.