[build-script] Disable lldb unit tests in PR testing
[build-script] Disable lldb unit tests in PR testing

There is some unresolved flakiness with the unit tests on Linux, which
we don't want interfering with PR testing. See:
https://github.com/apple/swift-lldb/pull/306

atrick/swift,hooman/swift,zisko/swift,allevato/swift,gribozavr/swift,JGiola/swift,harlanhaskins/swift,karwa/swift,rudkx/swift,ahoppen/swift,ahoppen/swift,alblue/swift,zisko/swift,shajrawi/swift,xedin/swift,amraboelela/swift,parkera/swift,karwa/swift,brentdax/swift,aschwaighofer/swift,glessard/swift,xedin/swift,shajrawi/swift,ahoppen/swift,CodaFi/swift,brentdax/swift,huonw/swift,danielmartin/swift,karwa/swift,JGiola/swift,JGiola/swift,shahmishal/swift,xwu/swift,jopamer/swift,austinzheng/swift,jckarter/swift,JGiola/swift,glessard/swift,sschiau/swift,apple/swift,sschiau/swift,ahoppen/swift,practicalswift/swift,shahmishal/swift,karwa/swift,allevato/swift,shahmishal/swift,xedin/swift,alblue/swift,devincoughlin/swift,lorentey/swift,sschiau/swift,tkremenek/swift,shahmishal/swift,practicalswift/swift,danielmartin/swift,sschiau/swift,lorentey/swift,allevato/swift,natecook1000/swift,huonw/swift,atrick/swift,shajrawi/swift,lorentey/swift,xwu/swift,karwa/swift,tkremenek/swift,amraboelela/swift,tjw/swift,zisko/swift,hooman/swift,apple/swift,jmgc/swift,natecook1000/swift,hooman/swift,stephentyrone/swift,shahmishal/swift,jopamer/swift,allevato/swift,alblue/swift,jopamer/swift,shahmishal/swift,devincoughlin/swift,jmgc/swift,nathawes/swift,stephentyrone/swift,glessard/swift,jckarter/swift,practicalswift/swift,stephentyrone/swift,jopamer/swift,nathawes/swift,rudkx/swift,lorentey/swift,hooman/swift,harlanhaskins/swift,gribozavr/swift,allevato/swift,karwa/swift,brentdax/swift,practicalswift/swift,karwa/swift,hooman/swift,rudkx/swift,CodaFi/swift,devincoughlin/swift,practicalswift/swift,stephentyrone/swift,atrick/swift,tjw/swift,allevato/swift,rudkx/swift,alblue/swift,natecook1000/swift,tjw/swift,roambotics/swift,practicalswift/swift,roambotics/swift,xwu/swift,jckarter/swift,tkremenek/swift,jmgc/swift,benlangmuir/swift,roambotics/swift,jmgc/swift,airspeedswift/swift,benlangmuir/swift,danielmartin/swift,nathawes/swift,parkera/swift,huonw/swift,gregomni/swift,shajrawi/swift,gregomni/swift,CodaFi/swift,roambotics/swift,gribozavr/swift,CodaFi/swift,harlanhaskins/swift,devincoughlin/swift,airspeedswift/swift,benlangmuir/swift,glessard/swift,brentdax/swift,aschwaighofer/swift,shajrawi/swift,huonw/swift,JGiola/swift,harlanhaskins/swift,CodaFi/swift,shajrawi/swift,xedin/swift,xedin/swift,natecook1000/swift,tkremenek/swift,nathawes/swift,gribozavr/swift,stephentyrone/swift,natecook1000/swift,danielmartin/swift,huonw/swift,austinzheng/swift,ahoppen/swift,gregomni/swift,aschwaighofer/swift,amraboelela/swift,amraboelela/swift,brentdax/swift,atrick/swift,benlangmuir/swift,brentdax/swift,stephentyrone/swift,tjw/swift,harlanhaskins/swift,CodaFi/swift,xedin/swift,parkera/swift,natecook1000/swift,austinzheng/swift,gregomni/swift,gribozavr/swift,amraboelela/swift,gribozavr/swift,shahmishal/swift,devincoughlin/swift,gribozavr/swift,danielmartin/swift,zisko/swift,amraboelela/swift,jopamer/swift,austinzheng/swift,aschwaighofer/swift,parkera/swift,danielmartin/swift,JGiola/swift,brentdax/swift,gribozavr/swift,roambotics/swift,zisko/swift,devincoughlin/swift,jckarter/swift,ahoppen/swift,parkera/swift,jckarter/swift,shahmishal/swift,alblue/swift,amraboelela/swift,jopamer/swift,roambotics/swift,devincoughlin/swift,atrick/swift,allevato/swift,xedin/swift,xwu/swift,xwu/swift,gregomni/swift,huonw/swift,devincoughlin/swift,alblue/swift,nathawes/swift,aschwaighofer/swift,alblue/swift,jckarter/swift,tjw/swift,glessard/swift,airspeedswift/swift,tjw/swift,benlangmuir/swift,xwu/swift,hooman/swift,nathawes/swift,parkera/swift,harlanhaskins/swift,aschwaighofer/swift,xedin/swift,apple/swift,airspeedswift/swift,jmgc/swift,tjw/swift,zisko/swift,danielmartin/swift,airspeedswift/swift,airspeedswift/swift,stephentyrone/swift,rudkx/swift,shajrawi/swift,parkera/swift,sschiau/swift,nathawes/swift,apple/swift,tkremenek/swift,rudkx/swift,austinzheng/swift,airspeedswift/swift,parkera/swift,jmgc/swift,zisko/swift,jmgc/swift,jopamer/swift,sschiau/swift,gregomni/swift,lorentey/swift,huonw/swift,karwa/swift,sschiau/swift,practicalswift/swift,lorentey/swift,austinzheng/swift,glessard/swift,aschwaighofer/swift,natecook1000/swift,lorentey/swift,practicalswift/swift,shajrawi/swift,sschiau/swift,tkremenek/swift,xwu/swift,harlanhaskins/swift,apple/swift,CodaFi/swift,atrick/swift,lorentey/swift,hooman/swift,apple/swift,jckarter/swift,tkremenek/swift,austinzheng/swift,benlangmuir/swift