go/loader: define a FindPackage hook for build systems not compatible with "go build".

Google's proprietary build system, for example, does not use the
_test.go suffix to distinguish test from non-test files; this
information is stated explicitly in another form.

Change-Id: I3a8e919dbc556b6d5cfea1d2123da2616bd934d4
Reviewed-on: https://go-review.googlesource.com/5450
Reviewed-by: David Crawshaw <crawshaw@golang.org>
1 file changed