runtime: detect errors in DuplicateHandle
These functions rely on DuplicateHandle succeeding, but they don't check
the return value, which might be masking subtle bugs that cause other
problems down the line.
Updates #43720.
Change-Id: I77f0e6645affa534777ffc173144a52e4afa5f81
Reviewed-on: https://go-review.googlesource.com/c/go/+/284135
Run-TryBot: Jason A. Donenfeld <Jason@zx2c4.com>
Reviewed-by: Alex Brainman <alex.brainman@gmail.com>
Reviewed-by: Austin Clements <austin@google.com>
Trust: Alex Brainman <alex.brainman@gmail.com>
Trust: Jason A. Donenfeld <Jason@zx2c4.com>