sweet/benchmarks/go-build: pass through stdout/stderr
sweet/benchmarks/go-build: pass through stdout/stderr

In case systemd-run fails, we'd like to see the error in results.

For golang/go#54760.

Change-Id: Id19d938308d25cf37bbb9e129ce1ec9e89ac8726
Reviewed-on: https://go-review.googlesource.com/c/benchmarks/+/426237
Run-TryBot: Michael Pratt <e7f1edc6d5aa9f6c8c377425db8f1a5816cbbb88@google.com>
Reviewed-by: Michael Knyszek <4473450dc5c88f06e1fb787f303d7805ec2aee65@google.com>
TryBot-Result: Gopher Robot <66cb808b70d30c07676d5e946fee83fd561249e5@golang.org>

golang/benchmarks,golang/benchmarks