sweet: discard stderr from List and enforce GOROOT in common.Go
This change resolves two issues in how Sweet runs on the builders:
1. List calls CombinedOutput to get its output, but the Go tool may
write "go: downloading ..." lines to stderr, breaking callers.
To fix this, call Output instead.
2. Like how cmd/bench needs to enforce the right GOROOT because the one
from the environment may be wrong for some toolchain, Sweet neglected
to do this too. So, set the right GOROOT for any common.Go that's
created in Sweet.
Together, these fixes should allow Sweet to run on the perf builder
Trust: Michael Knyszek <email@example.com>
Run-TryBot: Michael Knyszek <firstname.lastname@example.org>
TryBot-Result: Gopher Robot <email@example.com>
Reviewed-by: Michael Pratt <firstname.lastname@example.org>
3 files changed