Fix test build when VS is not installed on the root drive
Fix test build when VS is not installed on the root drive

closes #344

syeerzy/visualfsharp,cloudRoutine/FSharp.Compiler.Service,forki/FSharp.Compiler.Service,In2TheWild/fsharp,dsyme/fsharp,Jand42/FSharp.Compiler.Service,fsharp/fsharp,syeerzy/visualfsharp,sergey-tihon/FSharp.Compiler.Service,0x53A/FSharp.Compiler.Service,yever/FSharp.Compiler.Service,mafiya69/fsharp,rojepp/FSharp.Compiler.Service,brettfo/visualfsharp,vasily-kirichenko/FSharp.Compiler.Service,In2TheWild/fsharp,rneatherway/FSharp.Compiler.Service,fsharp/fsharp,0x53A/FSharp.Compiler.Service,syeerzy/visualfsharp,ncave/FSharp.Compiler.Service,ncave/FSharp.Compiler.Service,brettfo/visualfsharp,matthid/FSharp.Compiler.Service,mafiya69/fsharp,eloraiby/fsharp,alfonsogarciacaro/FSharp.Compiler.Service,dsyme/fsharp,vasily-kirichenko/FSharp.Compiler.Service,dsyme/fsharp,wk-j/fsharp,forki/FSharp.Compiler.Service,Heather/fsharp,dsyme/fsharp,syeerzy/visualfsharp,dsyme/FSharp.Compiler.Service,syeerzy/visualfsharp,sergey-tihon/FSharp.Compiler.Service,BillHally/FSharp.Compiler.Service,Jand42/FSharp.Compiler.Service,syeerzy/visualfsharp,cloudRoutine/FSharp.Compiler.Service,forki/FSharp.Compiler.Service,wk-j/fsharp,Jand42/FSharp.Compiler.Service,brettfo/visualfsharp,dsyme/FSharp.Compiler.Service,sergey-tihon/FSharp.Compiler.Service,cloudRoutine/FSharp.Compiler.Service,dsyme/fsharp,fsharp/fsharp,dsyme/fsharp,ncave/FSharp.Compiler.Service,rojepp/FSharp.Compiler.Service,brettfo/visualfsharp,dsyme/fsharp,brettfo/visualfsharp,rneatherway/FSharp.Compiler.Service,Heather/fsharp,yever/FSharp.Compiler.Service,matthid/FSharp.Compiler.Service,vasily-kirichenko/FSharp.Compiler.Service,matthid/FSharp.Compiler.Service,0x53A/FSharp.Compiler.Service,alfonsogarciacaro/FSharp.Compiler.Service,eloraiby/fsharp,brettfo/visualfsharp,alfonsogarciacaro/FSharp.Compiler.Service,BillHally/FSharp.Compiler.Service,dsyme/FSharp.Compiler.Service,rojepp/FSharp.Compiler.Service