named won't start on Windows

Nearly all Windows system tests fail on main since February 19 like this:

S:acl:2021-02-22T20:20:39-0800
T:acl:1:A
A:acl:System test acl
I:acl:PORTS:5322,5323,5324,5325,5326,5327,5328,5329,5330,5331,5332,5333,5334
I:acl:starting servers
I:acl:Couldn't start server C:/builds/isc-projects/bind9/Build/Release/named.exe -D acl-ns2 -X named.lock -m record,size,mctx -c named.conf -d 99 -g -U 4 -T maxcachesize=2097152 >named.run 2>&1 & echo $! (pid=2678)
I:acl:failed
kill: 2678: No such process
I:acl:starting servers failed
R:acl:FAIL
E:acl:2021-02-22T20:20:56-0800

I'll investigate further.