[cmake] Add the SDK directory after the toolchain directory when compiling host swift code.
[cmake] Add the SDK directory after the toolchain directory when compiling host swift code.

This ensures that we pick up libraries from the toolchain before picking up
libraries from the SDK we are using. Normally it would not matter the order that
we add these -L files since the contents of the SDK and toolchain are
disjoint. Once we begin performing stage2 swift builds though, we no longer have
this property since we pass in the stage1's installed libraries as the SDK
directory and we have not split the two sets of libraries yet. The end result is
that if we have the -L in the previous order, we will pick up just built
compatibility libraries before we pick up the actual compatibility libraries
from the actual toolchain we are using to compile. This results in compilation
breakage.

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