build: Fix regression introduced in PR23603
build: Fix regression introduced in PR23603

Assignments in builders/darwin.mk actually override previous assignments
in hosts/default.mk. Therefore, the append operator must be used
instead.

mm-s/bitcoin,namecoin/namecoin-core,GroestlCoin/GroestlCoin,particl/particl-core,bitcoinsSG/bitcoin,domob1812/namecore,Xekyo/bitcoin,tecnovert/particl-core,fanquake/bitcoin,jamesob/bitcoin,fanquake/bitcoin,particl/particl-core,Xekyo/bitcoin,namecoin/namecoin-core,domob1812/bitcoin,andreaskern/bitcoin,GroestlCoin/bitcoin,lateminer/bitcoin,achow101/bitcoin,sipsorcery/bitcoin,bitcoinknots/bitcoin,jambolo/bitcoin,mruddy/bitcoin,tecnovert/particl-core,GroestlCoin/bitcoin,jambolo/bitcoin,mruddy/bitcoin,mruddy/bitcoin,bitcoinknots/bitcoin,lateminer/bitcoin,AkioNak/bitcoin,GroestlCoin/bitcoin,tecnovert/particl-core,jlopp/statoshi,pataquets/namecoin-core,andreaskern/bitcoin,bitcoinknots/bitcoin,namecoin/namecore,dscotese/bitcoin,domob1812/bitcoin,bitcoin/bitcoin,andreaskern/bitcoin,domob1812/namecore,ajtowns/bitcoin,jlopp/statoshi,jamesob/bitcoin,achow101/bitcoin,jambolo/bitcoin,mm-s/bitcoin,kallewoof/bitcoin,kallewoof/bitcoin,anditto/bitcoin,AkioNak/bitcoin,domob1812/namecore,AkioNak/bitcoin,andreaskern/bitcoin,particl/particl-core,jlopp/statoshi,sipsorcery/bitcoin,instagibbs/bitcoin,instagibbs/bitcoin,GroestlCoin/bitcoin,fanquake/bitcoin,kallewoof/bitcoin,mm-s/bitcoin,jambolo/bitcoin,GroestlCoin/GroestlCoin,fujicoin/fujicoin,namecoin/namecoin-core,fujicoin/fujicoin,kallewoof/bitcoin,GroestlCoin/GroestlCoin,sstone/bitcoin,bitcoinsSG/bitcoin,sstone/bitcoin,achow101/bitcoin,domob1812/bitcoin,sipsorcery/bitcoin,mm-s/bitcoin,andreaskern/bitcoin,namecoin/namecore,pataquets/namecoin-core,Xekyo/bitcoin,pataquets/namecoin-core,mm-s/bitcoin,sstone/bitcoin,achow101/bitcoin,ajtowns/bitcoin,namecoin/namecoin-core,bitcoin/bitcoin,instagibbs/bitcoin,domob1812/bitcoin,Xekyo/bitcoin,bitcoin/bitcoin,particl/particl-core,lateminer/bitcoin,GroestlCoin/GroestlCoin,dscotese/bitcoin,bitcoinknots/bitcoin,sipsorcery/bitcoin,namecoin/namecoin-core,instagibbs/bitcoin,anditto/bitcoin,jambolo/bitcoin,domob1812/namecore,fanquake/bitcoin,namecoin/namecore,ajtowns/bitcoin,mm-s/bitcoin,bitcoinsSG/bitcoin,sstone/bitcoin,lateminer/bitcoin,dscotese/bitcoin,namecoin/namecore,anditto/bitcoin,bitcoinsSG/bitcoin,fujicoin/fujicoin,fanquake/bitcoin,GroestlCoin/GroestlCoin,achow101/bitcoin,instagibbs/bitcoin,domob1812/namecore,particl/particl-core,sipsorcery/bitcoin,kallewoof/bitcoin,dscotese/bitcoin,GroestlCoin/GroestlCoin,AkioNak/bitcoin,fujicoin/fujicoin,mruddy/bitcoin,achow101/bitcoin,dscotese/bitcoin,mruddy/bitcoin,fujicoin/fujicoin,andreaskern/bitcoin,instagibbs/bitcoin,bitcoinsSG/bitcoin,bitcoin/bitcoin,tecnovert/particl-core,sstone/bitcoin,lateminer/bitcoin,bitcoin/bitcoin,ajtowns/bitcoin,domob1812/bitcoin,particl/particl-core,tecnovert/particl-core,anditto/bitcoin,jlopp/statoshi,namecoin/namecoin-core,Xekyo/bitcoin,pataquets/namecoin-core,AkioNak/bitcoin,ajtowns/bitcoin,jlopp/statoshi,dscotese/bitcoin,jambolo/bitcoin,jamesob/bitcoin,GroestlCoin/bitcoin,bitcoinknots/bitcoin,mruddy/bitcoin,anditto/bitcoin,AkioNak/bitcoin,bitcoin/bitcoin,jamesob/bitcoin,sstone/bitcoin,pataquets/namecoin-core,lateminer/bitcoin,tecnovert/particl-core,jlopp/statoshi,GroestlCoin/bitcoin,kallewoof/bitcoin,domob1812/bitcoin,Xekyo/bitcoin,domob1812/namecore,jamesob/bitcoin,sipsorcery/bitcoin,anditto/bitcoin,namecoin/namecore,pataquets/namecoin-core,bitcoinsSG/bitcoin,ajtowns/bitcoin,fujicoin/fujicoin,jamesob/bitcoin,namecoin/namecore,fanquake/bitcoin