x_tests can access exports from the test variant of the package under
test. Change loadExportsFromFiles to understand that mode, and use it
where appropriate.
I didn't want to come up with a cache key for for the test variant, so
for now we bypass the cache in these situations.
Fixesgolang/go#29979.
Change-Id: I9959a08da97bbee64c5bcd56e06f548486693156
Reviewed-on: https://go-review.googlesource.com/c/tools/+/213221
Run-TryBot: Heschi Kreinick <heschi@google.com>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Rebecca Stambler <rstambler@golang.org>
