[build-script-impl] Remove three FIXME which removed build products.
[build-script-impl] Remove three FIXME which removed build products.

Dispatch, Foundation and XCTest build using CMake since a couple of
months ago, so there's no need to remove the partial results before
building anymore. This should make rebuilding a little bit faster.

gregomni/swift,harlanhaskins/swift,devincoughlin/swift,rudkx/swift,harlanhaskins/swift,xedin/swift,CodaFi/swift,ahoppen/swift,jmgc/swift,hooman/swift,gribozavr/swift,parkera/swift,karwa/swift,CodaFi/swift,CodaFi/swift,ahoppen/swift,gregomni/swift,shahmishal/swift,lorentey/swift,airspeedswift/swift,jckarter/swift,shajrawi/swift,glessard/swift,karwa/swift,JGiola/swift,jckarter/swift,JGiola/swift,jckarter/swift,devincoughlin/swift,jmgc/swift,aschwaighofer/swift,apple/swift,gregomni/swift,xedin/swift,CodaFi/swift,shahmishal/swift,CodaFi/swift,harlanhaskins/swift,benlangmuir/swift,CodaFi/swift,glessard/swift,hooman/swift,stephentyrone/swift,glessard/swift,airspeedswift/swift,allevato/swift,allevato/swift,shahmishal/swift,shajrawi/swift,devincoughlin/swift,jckarter/swift,shajrawi/swift,glessard/swift,tkremenek/swift,shahmishal/swift,nathawes/swift,parkera/swift,nathawes/swift,lorentey/swift,jmgc/swift,gribozavr/swift,rudkx/swift,stephentyrone/swift,shahmishal/swift,allevato/swift,stephentyrone/swift,benlangmuir/swift,parkera/swift,lorentey/swift,shajrawi/swift,rudkx/swift,nathawes/swift,xwu/swift,sschiau/swift,sschiau/swift,allevato/swift,parkera/swift,shahmishal/swift,xedin/swift,gribozavr/swift,roambotics/swift,parkera/swift,devincoughlin/swift,aschwaighofer/swift,gribozavr/swift,tkremenek/swift,apple/swift,gribozavr/swift,sschiau/swift,xwu/swift,jckarter/swift,tkremenek/swift,aschwaighofer/swift,harlanhaskins/swift,karwa/swift,gribozavr/swift,gribozavr/swift,roambotics/swift,parkera/swift,benlangmuir/swift,airspeedswift/swift,xedin/swift,rudkx/swift,tkremenek/swift,ahoppen/swift,JGiola/swift,lorentey/swift,nathawes/swift,apple/swift,tkremenek/swift,nathawes/swift,stephentyrone/swift,karwa/swift,tkremenek/swift,hooman/swift,xwu/swift,shajrawi/swift,airspeedswift/swift,nathawes/swift,airspeedswift/swift,aschwaighofer/swift,apple/swift,xwu/swift,allevato/swift,hooman/swift,sschiau/swift,ahoppen/swift,shajrawi/swift,allevato/swift,xwu/swift,gregomni/swift,stephentyrone/swift,rudkx/swift,gribozavr/swift,stephentyrone/swift,xedin/swift,xedin/swift,sschiau/swift,sschiau/swift,jckarter/swift,JGiola/swift,jmgc/swift,JGiola/swift,CodaFi/swift,xedin/swift,shajrawi/swift,atrick/swift,benlangmuir/swift,karwa/swift,apple/swift,glessard/swift,karwa/swift,aschwaighofer/swift,jckarter/swift,gregomni/swift,tkremenek/swift,lorentey/swift,hooman/swift,JGiola/swift,sschiau/swift,devincoughlin/swift,roambotics/swift,hooman/swift,ahoppen/swift,parkera/swift,rudkx/swift,roambotics/swift,harlanhaskins/swift,shahmishal/swift,xedin/swift,karwa/swift,allevato/swift,devincoughlin/swift,atrick/swift,airspeedswift/swift,karwa/swift,airspeedswift/swift,hooman/swift,nathawes/swift,aschwaighofer/swift,aschwaighofer/swift,devincoughlin/swift,harlanhaskins/swift,harlanhaskins/swift,lorentey/swift,shahmishal/swift,jmgc/swift,roambotics/swift,gregomni/swift,parkera/swift,xwu/swift,shajrawi/swift,stephentyrone/swift,lorentey/swift,xwu/swift,glessard/swift,jmgc/swift,apple/swift,lorentey/swift,benlangmuir/swift,ahoppen/swift,atrick/swift,sschiau/swift,atrick/swift,atrick/swift,roambotics/swift,benlangmuir/swift,jmgc/swift,devincoughlin/swift,atrick/swift