depends: Propagate well-known vars into depends
depends: Propagate well-known vars into depends

For example, doing:

  make CC=clang CXX=clang++

Should now propagate these settings down to depends packages

alecalve/bitcoin,jnewbery/bitcoin,namecoin/namecoin-core,pataquets/namecoin-core,mruddy/bitcoin,jonasschnelli/bitcoin,Xekyo/bitcoin,andreaskern/bitcoin,practicalswift/bitcoin,practicalswift/bitcoin,instagibbs/bitcoin,litecoin-project/litecoin,bitcoinsSG/bitcoin,sipsorcery/bitcoin,qtumproject/qtum,namecoin/namecoin-core,ElementsProject/elements,sipsorcery/bitcoin,jonasschnelli/bitcoin,MeshCollider/bitcoin,namecoin/namecore,practicalswift/bitcoin,kallewoof/bitcoin,Sjors/bitcoin,lateminer/bitcoin,fanquake/bitcoin,jamesob/bitcoin,ajtowns/bitcoin,practicalswift/bitcoin,mruddy/bitcoin,pstratem/bitcoin,jlopp/statoshi,achow101/bitcoin,bitcoin/bitcoin,qtumproject/qtum,alecalve/bitcoin,domob1812/bitcoin,namecoin/namecoin-core,Xekyo/bitcoin,rnicoll/dogecoin,particl/particl-core,fanquake/bitcoin,alecalve/bitcoin,jnewbery/bitcoin,litecoin-project/litecoin,jambolo/bitcoin,andreaskern/bitcoin,AkioNak/bitcoin,sipsorcery/bitcoin,kallewoof/bitcoin,Sjors/bitcoin,fujicoin/fujicoin,dscotese/bitcoin,JeremyRubin/bitcoin,practicalswift/bitcoin,mruddy/bitcoin,n1bor/bitcoin,midnightmagic/bitcoin,rnicoll/bitcoin,prusnak/bitcoin,anditto/bitcoin,instagibbs/bitcoin,lateminer/bitcoin,tecnovert/particl-core,fujicoin/fujicoin,EthanHeilman/bitcoin,MarcoFalke/bitcoin,GroestlCoin/bitcoin,bitcoinsSG/bitcoin,cdecker/bitcoin,fanquake/bitcoin,lateminer/bitcoin,GroestlCoin/bitcoin,sstone/bitcoin,fanquake/bitcoin,GroestlCoin/bitcoin,mm-s/bitcoin,MarcoFalke/bitcoin,kallewoof/bitcoin,yenliangl/bitcoin,particl/particl-core,midnightmagic/bitcoin,jnewbery/bitcoin,MarcoFalke/bitcoin,dscotese/bitcoin,namecoin/namecoin-core,AkioNak/bitcoin,tecnovert/particl-core,particl/particl-core,cdecker/bitcoin,ajtowns/bitcoin,bitcoinsSG/bitcoin,Sjors/bitcoin,sstone/bitcoin,qtumproject/qtum,domob1812/namecore,EthanHeilman/bitcoin,AkioNak/bitcoin,Xekyo/bitcoin,rnicoll/dogecoin,yenliangl/bitcoin,practicalswift/bitcoin,anditto/bitcoin,domob1812/bitcoin,JeremyRubin/bitcoin,litecoin-project/litecoin,qtumproject/qtum,lateminer/bitcoin,yenliangl/bitcoin,yenliangl/bitcoin,n1bor/bitcoin,EthanHeilman/bitcoin,sstone/bitcoin,fanquake/bitcoin,rnicoll/dogecoin,rnicoll/bitcoin,namecoin/namecore,ElementsProject/elements,jonasschnelli/bitcoin,prusnak/bitcoin,pstratem/bitcoin,pataquets/namecoin-core,namecoin/namecore,MarcoFalke/bitcoin,kallewoof/bitcoin,yenliangl/bitcoin,jambolo/bitcoin,n1bor/bitcoin,apoelstra/bitcoin,GroestlCoin/bitcoin,ajtowns/bitcoin,MarcoFalke/bitcoin,sstone/bitcoin,MeshCollider/bitcoin,MeshCollider/bitcoin,prusnak/bitcoin,bitcoinknots/bitcoin,fujicoin/fujicoin,prusnak/bitcoin,dscotese/bitcoin,rnicoll/dogecoin,JeremyRubin/bitcoin,andreaskern/bitcoin,andreaskern/bitcoin,ElementsProject/elements,jlopp/statoshi,mm-s/bitcoin,andreaskern/bitcoin,mm-s/bitcoin,sipsorcery/bitcoin,kallewoof/bitcoin,domob1812/namecore,qtumproject/qtum,Sjors/bitcoin,prusnak/bitcoin,pataquets/namecoin-core,particl/particl-core,andreaskern/bitcoin,jlopp/statoshi,namecoin/namecoin-core,Xekyo/bitcoin,bitcoinknots/bitcoin,apoelstra/bitcoin,JeremyRubin/bitcoin,n1bor/bitcoin,apoelstra/bitcoin,namecoin/namecoin-core,litecoin-project/litecoin,apoelstra/bitcoin,alecalve/bitcoin,GroestlCoin/GroestlCoin,MarcoFalke/bitcoin,particl/particl-core,ElementsProject/elements,pstratem/bitcoin,pstratem/bitcoin,mm-s/bitcoin,n1bor/bitcoin,ajtowns/bitcoin,namecoin/namecore,domob1812/namecore,dscotese/bitcoin,mruddy/bitcoin,tecnovert/particl-core,instagibbs/bitcoin,pataquets/namecoin-core,domob1812/bitcoin,GroestlCoin/GroestlCoin,jlopp/statoshi,midnightmagic/bitcoin,AkioNak/bitcoin,mm-s/bitcoin,fanquake/bitcoin,anditto/bitcoin,litecoin-project/litecoin,ajtowns/bitcoin,jonasschnelli/bitcoin,pataquets/namecoin-core,Xekyo/bitcoin,pstratem/bitcoin,achow101/bitcoin,GroestlCoin/GroestlCoin,jlopp/statoshi,alecalve/bitcoin,lateminer/bitcoin,n1bor/bitcoin,jamesob/bitcoin,instagibbs/bitcoin,jamesob/bitcoin,anditto/bitcoin,bitcoinknots/bitcoin,domob1812/namecore,bitcoin/bitcoin,EthanHeilman/bitcoin,instagibbs/bitcoin,jambolo/bitcoin,namecoin/namecore,bitcoinsSG/bitcoin,midnightmagic/bitcoin,bitcoin/bitcoin,achow101/bitcoin,jambolo/bitcoin,dscotese/bitcoin,mruddy/bitcoin,GroestlCoin/GroestlCoin,ajtowns/bitcoin,domob1812/bitcoin,bitcoinknots/bitcoin,qtumproject/qtum,alecalve/bitcoin,cdecker/bitcoin,mm-s/bitcoin,sipsorcery/bitcoin,fujicoin/fujicoin,qtumproject/qtum,MeshCollider/bitcoin,jnewbery/bitcoin,ElementsProject/elements,rnicoll/bitcoin,jambolo/bitcoin,sipsorcery/bitcoin,prusnak/bitcoin,tecnovert/particl-core,pataquets/namecoin-core,bitcoinsSG/bitcoin,bitcoinknots/bitcoin,jambolo/bitcoin,cdecker/bitcoin,GroestlCoin/GroestlCoin,particl/particl-core,Sjors/bitcoin,bitcoin/bitcoin,domob1812/namecore,rnicoll/bitcoin,jlopp/statoshi,rnicoll/bitcoin,anditto/bitcoin,lateminer/bitcoin,apoelstra/bitcoin,GroestlCoin/GroestlCoin,jonasschnelli/bitcoin,GroestlCoin/bitcoin,sstone/bitcoin,midnightmagic/bitcoin,domob1812/namecore,achow101/bitcoin,JeremyRubin/bitcoin,midnightmagic/bitcoin,tecnovert/particl-core,JeremyRubin/bitcoin,fujicoin/fujicoin,AkioNak/bitcoin,sstone/bitcoin,ElementsProject/elements,fujicoin/fujicoin,achow101/bitcoin,jnewbery/bitcoin,cdecker/bitcoin,rnicoll/dogecoin,jamesob/bitcoin,kallewoof/bitcoin,litecoin-project/litecoin,MeshCollider/bitcoin,Xekyo/bitcoin,rnicoll/bitcoin,dscotese/bitcoin,pstratem/bitcoin,GroestlCoin/bitcoin,yenliangl/bitcoin,bitcoin/bitcoin,namecoin/namecore,EthanHeilman/bitcoin,jamesob/bitcoin,EthanHeilman/bitcoin,instagibbs/bitcoin,bitcoinsSG/bitcoin,domob1812/bitcoin,achow101/bitcoin,AkioNak/bitcoin,mruddy/bitcoin,tecnovert/particl-core,cdecker/bitcoin,bitcoin/bitcoin,MeshCollider/bitcoin,domob1812/bitcoin,jamesob/bitcoin,apoelstra/bitcoin,anditto/bitcoin