Fix check for in_pktinfo and ip_mreqn (#23976)
Fix check for in_pktinfo and ip_mreqn (#23976)

This change fixes the check for in_pktinfo and ip_mreqn. It was broken and was
always succeeding even on platforms where these structs were not present.
Jiayili1/corefx,shimingsg/corefx,Ermiar/corefx,mmitche/corefx,wtgodbe/corefx,mmitche/corefx,Ermiar/corefx,tijoytom/corefx,shimingsg/corefx,ericstj/corefx,ViktorHofer/corefx,axelheer/corefx,tijoytom/corefx,mmitche/corefx,zhenlan/corefx,ericstj/corefx,BrennanConroy/corefx,mmitche/corefx,ravimeda/corefx,ericstj/corefx,seanshpark/corefx,Jiayili1/corefx,ravimeda/corefx,axelheer/corefx,Jiayili1/corefx,wtgodbe/corefx,Ermiar/corefx,parjong/corefx,twsouthwick/corefx,ViktorHofer/corefx,ericstj/corefx,Jiayili1/corefx,parjong/corefx,zhenlan/corefx,zhenlan/corefx,ViktorHofer/corefx,twsouthwick/corefx,BrennanConroy/corefx,tijoytom/corefx,fgreinacher/corefx,ravimeda/corefx,Ermiar/corefx,seanshpark/corefx,ericstj/corefx,BrennanConroy/corefx,seanshpark/corefx,shimingsg/corefx,Jiayili1/corefx,ericstj/corefx,Jiayili1/corefx,shimingsg/corefx,tijoytom/corefx,axelheer/corefx,Jiayili1/corefx,ptoonen/corefx,fgreinacher/corefx,ptoonen/corefx,twsouthwick/corefx,axelheer/corefx,tijoytom/corefx,ericstj/corefx,ravimeda/corefx,twsouthwick/corefx,ravimeda/corefx,zhenlan/corefx,seanshpark/corefx,shimingsg/corefx,twsouthwick/corefx,mmitche/corefx,wtgodbe/corefx,seanshpark/corefx,parjong/corefx,ViktorHofer/corefx,ravimeda/corefx,axelheer/corefx,zhenlan/corefx,tijoytom/corefx,Ermiar/corefx,fgreinacher/corefx,ptoonen/corefx,parjong/corefx,wtgodbe/corefx,ptoonen/corefx,ptoonen/corefx,wtgodbe/corefx,Ermiar/corefx,seanshpark/corefx,ViktorHofer/corefx,fgreinacher/corefx,wtgodbe/corefx,zhenlan/corefx,axelheer/corefx,parjong/corefx,tijoytom/corefx,wtgodbe/corefx,twsouthwick/corefx,parjong/corefx,ViktorHofer/corefx,zhenlan/corefx,twsouthwick/corefx,shimingsg/corefx,ViktorHofer/corefx,parjong/corefx,ptoonen/corefx,shimingsg/corefx,mmitche/corefx,ravimeda/corefx,ptoonen/corefx,Ermiar/corefx,mmitche/corefx,seanshpark/corefx