cmd/go: use cached source files in "go list -find -compiled"
When "go list" is invoked with -find, it clears the list of imports
for each package matched on the command line. This affects action IDs,
since they incorporate dependencies' action IDs. Consequently, the
build triggered by -compiled won't find sources cached by
"go build".
We can still safely cache compiled sources from multiple runs of
"go list -find -compiled" though, since cgo generated sources are not
affected by imported dependencies. This change adds a second look into
the cache in this situation.
Fixes #29371
Change-Id: Ia0ae5a403ab5d621feaa16f521e6a65ac0ae6d9a
Reviewed-on: https://go-review.googlesource.com/c/155481 Reviewed-by: Bryan C. Mills <bcmills@google.com>