Thank you Adam for this update!
I have now the following messages when I try to fetch. Do you have an 
idea?
$ bmake fetch
=> Bootstrap dependency digest>=20010302: found digest-20190127
=> Fetching cmake-3.16.2.tar.gz
=> Total size: 9109837 bytes
Certificate verification failed for /C=US/O=Let's Encrypt/CN=Let's 
Encrypt Authority X3
34370572288:error:1416F086:SSL 
routines:tls_process_server_certificate:certificate verify 
failed:/usr/src/crypto/openssl/ssl/statem/statem_clnt.c:1925:
fetch: https://cmake.org/files/v3.16/cmake-3.16.2.tar.gz: 
Authentication error
fetch: Unable to fetch expected file cmake-3.16.2.tar.gz
fetch: http://cdn.NetBSD.org/pub/pkgsrc/distfiles/cmake-3.16.2.tar.gz: 
Not Found
fetch: Unable to fetch expected file cmake-3.16.2.tar.gz
fetch: 
http://ftp6.NetBSD.org/pub/pkgsrc/distfiles/cmake-3.16.2.tar.gz: Not 
Found
fetch: Unable to fetch expected file cmake-3.16.2.tar.gz
fetch: 
http://ftp.fr.NetBSD.org/pub/pkgsrc/distfiles/cmake-3.16.2.tar.gz: Not 
Found
fetch: Unable to fetch expected file cmake-3.16.2.tar.gz
fetch: http://ftp.NetBSD.org/pub/pkgsrc/distfiles/cmake-3.16.2.tar.gz: 
Not Found
fetch: Unable to fetch expected file cmake-3.16.2.tar.gz
*** Error code 1