Utility to generate the seeds.txt list that is compiled into the client (see src/chainparamsseeds.h and other utilities in contrib/seeds).
Be sure to update PATTERN_AGENT in makeseeds.py to include the current version,
and remove old versions as necessary (at a minimum when SeedsServiceFlags()
changes its default return value, as those are the services which seeds are added
to addrman with).
The seeds compiled into the release are created from DNS seed data, like this:
curl https://bitcoin.sipa.be/seeds.txt.gz | gzip -dc > seeds_main.txt
curl https://bitcoin.sipa.be/asmap-filled.dat > asmap-filled.dat
python3 makeseeds.py -a asmap-filled.dat -s seeds_main.txt > nodes_main.txt
cat nodes_main_manual.txt >> nodes_main.txt
python3 generate-seeds.py . > ../../src/chainparamsseeds.h