Adding switch to build.cmd to skip KRE install

Author: pranavkm

build.cmd

@@ -18,6 +18,8 @@ copy %CACHED_NUGET% .nuget\nuget.exe > nul
 IF EXIST packages\KoreBuild goto run
 .nuget\NuGet.exe install KoreBuild -ExcludeVersion -o packages -nocache -pre
 .nuget\NuGet.exe install Sake -version 0.2 -o packages -ExcludeVersion
+
+IF "%SKIP_KRE_INSTALL%"=="1" goto run
 CALL packages\KoreBuild\build\kvm upgrade -svr50 -x86
 CALL packages\KoreBuild\build\kvm install default -svrc50 -x86