Enable pinning build script

build.cmd

@@ -3,6 +3,8 @@ cd %~dp0
 
 SETLOCAL
 SET CACHED_NUGET=%LocalAppData%\NuGet\NuGet.exe
+SET BUILDCMD_KOREBUILD_VERSION=""
+SET BUILDCMD_DNX_VERSION=""
 
 IF EXIST %CACHED_NUGET% goto copynuget
 echo Downloading latest version of NuGet.exe...
@@ -16,11 +18,19 @@ copy %CACHED_NUGET% .nuget\nuget.exe > nul
 
 :restore
 IF EXIST packages\KoreBuild goto run
-.nuget\NuGet.exe install KoreBuild -ExcludeVersion -o packages -nocache -pre
+IF %BUILDCMD_KOREBUILD_VERSION%=="" (
+	.nuget\NuGet.exe install KoreBuild -ExcludeVersion -o packages -nocache -pre
+) ELSE (
+	.nuget\NuGet.exe install KoreBuild -version %BUILDCMD_KOREBUILD_VERSION% -ExcludeVersion -o packages -nocache -pre
+)
 .nuget\NuGet.exe install Sake -version 0.2 -o packages -ExcludeVersion
 
 IF "%SKIP_DNX_INSTALL%"=="1" goto run
-CALL packages\KoreBuild\build\dnvm upgrade -runtime CLR -arch x86
+IF %BUILDCMD_DNX_VERSION%=="" (
+	CALL packages\KoreBuild\build\dnvm upgrade -runtime CLR -arch x86
+) ELSE (
+	CALL packages\KoreBuild\build\dnvm install %BUILDCMD_DNX_VERSION% -runtime CLR -arch x86 -a default
+)
 CALL packages\KoreBuild\build\dnvm install default -runtime CoreCLR -arch x86
 
 :run