Fix crossfs build for armel jessie (#29268)
Fix crossfs build for armel jessie (#29268)

The source list was incorrectly containing stable/main sources in addition
to the jessie/main. That caused the openssl 1.1 to creep in and the
build with such crossfs was failing.
The reason why it was working in the past is that the stable branch used
to be something older and so it didn't have this issue.
shimingsg/corefx,shimingsg/corefx,ViktorHofer/corefx,BrennanConroy/corefx,ptoonen/corefx,Jiayili1/corefx,ViktorHofer/corefx,wtgodbe/corefx,ptoonen/corefx,ericstj/corefx,ViktorHofer/corefx,ericstj/corefx,wtgodbe/corefx,ViktorHofer/corefx,wtgodbe/corefx,mmitche/corefx,Jiayili1/corefx,Jiayili1/corefx,mmitche/corefx,Jiayili1/corefx,ptoonen/corefx,wtgodbe/corefx,wtgodbe/corefx,shimingsg/corefx,ptoonen/corefx,mmitche/corefx,mmitche/corefx,ericstj/corefx,shimingsg/corefx,ptoonen/corefx,ViktorHofer/corefx,ericstj/corefx,shimingsg/corefx,mmitche/corefx,ericstj/corefx,BrennanConroy/corefx,ViktorHofer/corefx,ptoonen/corefx,ericstj/corefx,wtgodbe/corefx,mmitche/corefx,Jiayili1/corefx,wtgodbe/corefx,shimingsg/corefx,ptoonen/corefx,BrennanConroy/corefx,mmitche/corefx,ViktorHofer/corefx,shimingsg/corefx,ericstj/corefx,Jiayili1/corefx,Jiayili1/corefx