make it so user cflags can override built-in ones
make it so user cflags can override built-in ones

AveRapina/visionworkbench,fengzhyuan/visionworkbench,DougFirErickson/visionworkbench,fengzhyuan/visionworkbench,AveRapina/visionworkbench,fengzhyuan/visionworkbench,fengzhyuan/visionworkbench,DougFirErickson/visionworkbench,AveRapina/visionworkbench,DougFirErickson/visionworkbench,DougFirErickson/visionworkbench,AveRapina/visionworkbench,DougFirErickson/visionworkbench,fengzhyuan/visionworkbench,fengzhyuan/visionworkbench,DougFirErickson/visionworkbench,AveRapina/visionworkbench,AveRapina/visionworkbench,fengzhyuan/visionworkbench