build: early exit on error

If build.ps1 fails, immediately exit rather than cleaning up. We may
lose the error code in such situations.

Author: compnerd

utils/build-windows-toolchain.bat

@@ -81,7 +81,7 @@ powershell.exe -ExecutionPolicy RemoteSigned -File %~dp0build.ps1 ^
   -BuildType %CMAKE_BUILD_TYPE% ^
   %SkipPackagingArg% ^
   %TestArg% ^
-  -Stage %PackageRoot%
+  -Stage %PackageRoot% || (exit /b)
 
 :: Clean up the module cache
 rd /s /q %LocalAppData%\clang\ModuleCache