gotools: copy golang.org/x/tools for vet test

The new vet command now depends on golang.org/x/tools.

Change-Id: I251553432a6865450a1da598b153ac94327f0295
Reviewed-on: https://go-review.googlesource.com/c/159197
Reviewed-by: Than McIntosh <thanm@google.com>

gotools/CMakeLists.txt

diff --git a/gotools/CMakeLists.txt b/gotools/CMakeLists.txt
index b7b9fd8..567747b 100644
--- a/gotools/CMakeLists.txt
+++ b/gotools/CMakeLists.txt
@@ -186,6 +186,7 @@
     "COPYDIRS"
         "${cmd_srcroot}/vet:src/cmd"
         "${cmd_srcroot}/internal/objabi:src/cmd/internal"
+        "${libgo_srcroot}/go/golang.org/x/tools:src/cmd/vendor/golang.org/x"
     "COPYFILES" "${libgo_binroot}/objabi.go:src/cmd/internal/objabi"
     "TIMEOUT" ${default_check_timeout}
     "GOC" "${rungoc}"