Implement FlushProcessWriteBuffers for Unix
Implement FlushProcessWriteBuffers for Unix

This change is a port of the FlushProcessWriteBuffers implementation from the CoreCLR.

mjp41/corert,yizhang82/corert,shrah/corert,yizhang82/corert,gregkalapos/corert,shrah/corert,yizhang82/corert,kyulee1/corert,kyulee1/corert,krytarowski/corert,tijoytom/corert,mjp41/corert,botaberg/corert,manu-silicon/corert,botaberg/corert,yizhang82/corert,gregkalapos/corert,mjp41/corert,schellap/corert,botaberg/corert,botaberg/corert,kyulee1/corert,kyulee1/corert,manu-silicon/corert,gregkalapos/corert,manu-silicon/corert,mjp41/corert,shrah/corert,krytarowski/corert,schellap/corert,krytarowski/corert,mjp41/corert,shrah/corert,schellap/corert,schellap/corert,manu-silicon/corert,sandreenko/corert,sandreenko/corert,gregkalapos/corert,manu-silicon/corert,tijoytom/corert,tijoytom/corert,sandreenko/corert,tijoytom/corert,krytarowski/corert,schellap/corert,sandreenko/corert