main.star: set gotestjsonbuildtext=1 GODEBUG globally at tip

Two reasons: to buy more time to work on the result_adapter/ResultDB
side (beyond just the bare minimum behavior of not regressing beyond
what we had before), and to test that using a GODEBUG for this works
as we expect. It already uncovered the need to merge multiple GODEBUG
settings that we hadn't run into earlier.

For golang/go#70402.

Change-Id: I9b86f6a5462637eef84f3efca9fc31d11657d756
Reviewed-on: https://go-review.googlesource.com/c/build/+/629375
Auto-Submit: Dmitri Shuralyov <[email protected]>
LUCI-TryBot-Result: Go LUCI <[email protected]>
Reviewed-by: Dmitri Shuralyov <[email protected]>
Reviewed-by: Michael Knyszek <[email protected]>

Author: dmitshur