build-script-impl: Generate the test commands from cmake and ninja in separate steps so that if the target does not exist the script will fail instead of continuing. `set -e` is supposed to fix this, but since the command is empty if the target doesn't exist, the subshell returns 0 and the script continues.
build-script-impl: Generate the test commands from cmake and ninja in
separate steps so that if the target does not exist the script will fail
instead of continuing. `set -e` is supposed to fix this, but since the
command is empty if the target doesn't exist, the subshell returns 0 and
the script continues.

Also, print out the cmake and ninja commands so that we don't hide so much
of the machinery.

Fixes rdar://problem/29003970

allevato/swift,calebd/swift,swiftix/swift,djwbrown/swift,aschwaighofer/swift,airspeedswift/swift,gregomni/swift,codestergit/swift,shajrawi/swift,kstaring/swift,djwbrown/swift,ben-ng/swift,zisko/swift,brentdax/swift,manavgabhawala/swift,sschiau/swift,stephentyrone/swift,calebd/swift,nathawes/swift,therealbnut/swift,lorentey/swift,roambotics/swift,gottesmm/swift,swiftix/swift,shahmishal/swift,karwa/swift,huonw/swift,bitjammer/swift,bitjammer/swift,zisko/swift,amraboelela/swift,tardieu/swift,danielmartin/swift,karwa/swift,deyton/swift,nathawes/swift,apple/swift,atrick/swift,swiftix/swift,xedin/swift,practicalswift/swift,jckarter/swift,kstaring/swift,xedin/swift,harlanhaskins/swift,stephentyrone/swift,alblue/swift,ahoppen/swift,calebd/swift,arvedviehweger/swift,atrick/swift,CodaFi/swift,tinysun212/swift-windows,glessard/swift,JaSpa/swift,hughbe/swift,brentdax/swift,atrick/swift,deyton/swift,practicalswift/swift,gregomni/swift,jopamer/swift,codestergit/swift,deyton/swift,gribozavr/swift,alblue/swift,tjw/swift,xwu/swift,JaSpa/swift,manavgabhawala/swift,hooman/swift,lorentey/swift,Jnosh/swift,swiftix/swift,parkera/swift,practicalswift/swift,devincoughlin/swift,tjw/swift,JaSpa/swift,uasys/swift,tkremenek/swift,nathawes/swift,harlanhaskins/swift,sschiau/swift,devincoughlin/swift,karwa/swift,jopamer/swift,CodaFi/swift,frootloops/swift,codestergit/swift,allevato/swift,bitjammer/swift,manavgabhawala/swift,felix91gr/swift,xwu/swift,allevato/swift,jckarter/swift,airspeedswift/swift,gmilos/swift,tinysun212/swift-windows,gribozavr/swift,xwu/swift,JGiola/swift,frootloops/swift,devincoughlin/swift,OscarSwanros/swift,zisko/swift,gmilos/swift,uasys/swift,ben-ng/swift,shahmishal/swift,natecook1000/swift,Jnosh/swift,calebd/swift,JGiola/swift,glessard/swift,benlangmuir/swift,milseman/swift,austinzheng/swift,natecook1000/swift,glessard/swift,xwu/swift,lorentey/swift,jtbandes/swift,aschwaighofer/swift,codestergit/swift,danielmartin/swift,danielmartin/swift,glessard/swift,gottesmm/swift,aschwaighofer/swift,stephentyrone/swift,milseman/swift,natecook1000/swift,airspeedswift/swift,benlangmuir/swift,tkremenek/swift,arvedviehweger/swift,therealbnut/swift,huonw/swift,hooman/swift,huonw/swift,xwu/swift,therealbnut/swift,zisko/swift,devincoughlin/swift,austinzheng/swift,devincoughlin/swift,gottesmm/swift,JGiola/swift,brentdax/swift,apple/swift,manavgabhawala/swift,tkremenek/swift,danielmartin/swift,austinzheng/swift,therealbnut/swift,milseman/swift,shahmishal/swift,stephentyrone/swift,gregomni/swift,nathawes/swift,gmilos/swift,gottesmm/swift,jmgc/swift,parkera/swift,shajrawi/swift,tjw/swift,stephentyrone/swift,benlangmuir/swift,gribozavr/swift,harlanhaskins/swift,parkera/swift,aschwaighofer/swift,stephentyrone/swift,return/swift,austinzheng/swift,gmilos/swift,airspeedswift/swift,shahmishal/swift,Jnosh/swift,allevato/swift,huonw/swift,jtbandes/swift,zisko/swift,rudkx/swift,ahoppen/swift,amraboelela/swift,swiftix/swift,jmgc/swift,xedin/swift,karwa/swift,felix91gr/swift,harlanhaskins/swift,lorentey/swift,kstaring/swift,ahoppen/swift,milseman/swift,manavgabhawala/swift,swiftix/swift,deyton/swift,jopamer/swift,CodaFi/swift,glessard/swift,kstaring/swift,jckarter/swift,tjw/swift,gribozavr/swift,gribozavr/swift,tinysun212/swift-windows,arvedviehweger/swift,benlangmuir/swift,hooman/swift,deyton/swift,harlanhaskins/swift,tardieu/swift,therealbnut/swift,codestergit/swift,xwu/swift,practicalswift/swift,jopamer/swift,gmilos/swift,CodaFi/swift,hooman/swift,amraboelela/swift,frootloops/swift,uasys/swift,tinysun212/swift-windows,hughbe/swift,aschwaighofer/swift,benlangmuir/swift,lorentey/swift,zisko/swift,return/swift,hooman/swift,frootloops/swift,tardieu/swift,aschwaighofer/swift,jmgc/swift,djwbrown/swift,sschiau/swift,manavgabhawala/swift,tardieu/swift,harlanhaskins/swift,sschiau/swift,allevato/swift,uasys/swift,brentdax/swift,calebd/swift,jckarter/swift,rudkx/swift,practicalswift/swift,uasys/swift,aschwaighofer/swift,tkremenek/swift,amraboelela/swift,danielmartin/swift,austinzheng/swift,jmgc/swift,nathawes/swift,tardieu/swift,return/swift,shajrawi/swift,djwbrown/swift,tjw/swift,apple/swift,milseman/swift,OscarSwanros/swift,alblue/swift,danielmartin/swift,calebd/swift,JaSpa/swift,hughbe/swift,austinzheng/swift,jtbandes/swift,natecook1000/swift,hughbe/swift,jopamer/swift,gregomni/swift,arvedviehweger/swift,swiftix/swift,huonw/swift,tardieu/swift,tjw/swift,shajrawi/swift,karwa/swift,JaSpa/swift,felix91gr/swift,CodaFi/swift,karwa/swift,airspeedswift/swift,lorentey/swift,tkremenek/swift,tinysun212/swift-windows,frootloops/swift,return/swift,nathawes/swift,tkremenek/swift,OscarSwanros/swift,deyton/swift,hooman/swift,kstaring/swift,sschiau/swift,ahoppen/swift,return/swift,JGiola/swift,xedin/swift,Jnosh/swift,practicalswift/swift,tinysun212/swift-windows,felix91gr/swift,bitjammer/swift,gmilos/swift,djwbrown/swift,milseman/swift,alblue/swift,devincoughlin/swift,ben-ng/swift,jopamer/swift,parkera/swift,danielmartin/swift,therealbnut/swift,therealbnut/swift,zisko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