[NFC] [SILOpt] Explicitly specified flag defaults.
[NFC] [SILOpt] Explicitly specified flag defaults.

In preparation to change the default values, specify explicitly what
they are.

roambotics/swift,apple/swift,JGiola/swift,gregomni/swift,rudkx/swift,JGiola/swift,atrick/swift,atrick/swift,atrick/swift,gregomni/swift,JGiola/swift,roambotics/swift,JGiola/swift,roambotics/swift,rudkx/swift,apple/swift,benlangmuir/swift,glessard/swift,gregomni/swift,atrick/swift,ahoppen/swift,ahoppen/swift,rudkx/swift,roambotics/swift,rudkx/swift,benlangmuir/swift,glessard/swift,gregomni/swift,atrick/swift,benlangmuir/swift,benlangmuir/swift,rudkx/swift,apple/swift,glessard/swift,ahoppen/swift,apple/swift,glessard/swift,glessard/swift,roambotics/swift,JGiola/swift,ahoppen/swift,gregomni/swift,gregomni/swift,glessard/swift,apple/swift,apple/swift,rudkx/swift,roambotics/swift,JGiola/swift,benlangmuir/swift,ahoppen/swift,benlangmuir/swift,ahoppen/swift,atrick/swift