Exit the build script if Hadrian cannot be built

build.stack.bat

 @rem Change the current directory to the one containing this script
 @cd %~dp0
 
-@rem Build Hadrian and dependencies
+@rem Build Hadrian and dependencies and exit the script if the build failed
 @stack build
+@if %errorlevel% neq 0 exit /B %errorlevel%
 
 @rem Run Hadrian in GHC top directory forwarding additional user arguments
 @stack exec hadrian -- --lint --directory ".." %*