[build-script-impl] Add a comment explaining why an option isn't truly dead as per reviewers suggestion.
[build-script-impl] Add a comment explaining why an option isn't truly dead as per reviewers suggestion.

In the original revert, this option was used in two places and I added a comment
only on the first one. This copies the comment onto the second usage of the
option.

Thanks to @edymtt and @compnerd for catching my careless error!

hooman/swift,atrick/swift,rudkx/swift,jmgc/swift,jmgc/swift,benlangmuir/swift,roambotics/swift,roambotics/swift,rudkx/swift,jmgc/swift,atrick/swift,xwu/swift,tkremenek/swift,JGiola/swift,glessard/swift,parkera/swift,tkremenek/swift,gregomni/swift,rudkx/swift,ahoppen/swift,benlangmuir/swift,nathawes/swift,glessard/swift,JGiola/swift,hooman/swift,parkera/swift,xwu/swift,glessard/swift,gregomni/swift,tkremenek/swift,parkera/swift,roambotics/swift,jmgc/swift,glessard/swift,apple/swift,jmgc/swift,benlangmuir/swift,nathawes/swift,roambotics/swift,gregomni/swift,glessard/swift,nathawes/swift,ahoppen/swift,rudkx/swift,tkremenek/swift,nathawes/swift,ahoppen/swift,nathawes/swift,atrick/swift,rudkx/swift,hooman/swift,rudkx/swift,apple/swift,nathawes/swift,xwu/swift,nathawes/swift,xwu/swift,JGiola/swift,tkremenek/swift,JGiola/swift,hooman/swift,xwu/swift,benlangmuir/swift,JGiola/swift,xwu/swift,JGiola/swift,roambotics/swift,roambotics/swift,parkera/swift,atrick/swift,gregomni/swift,ahoppen/swift,parkera/swift,apple/swift,apple/swift,tkremenek/swift,apple/swift,parkera/swift,parkera/swift,ahoppen/swift,benlangmuir/swift,benlangmuir/swift,ahoppen/swift,jmgc/swift,apple/swift,atrick/swift,gregomni/swift,hooman/swift,glessard/swift,parkera/swift,jmgc/swift,hooman/swift,tkremenek/swift,gregomni/swift,xwu/swift,atrick/swift,hooman/swift