[post-build] Allow passing additional parameters to sdk-task.ps1 invocation in the post-build yaml template

[riarenas]

The sdk-task.ps1 script allows passing of additional parameters to the msbuild invocations, but the post-build yaml template doesn't plumb those through.

@JohnTortugo suggested adding a new parameter to the post-build.yml template that will pass whatever additional parameters through.

CC @AaronRobinsonMSFT @JohnTortugo