vpn_manager: Calculate gmock/gtest library dependencies programatically

(gmock/gtest doesn't generate pkg-config metadata, calculating lib
 dependencies this way makes it easier to upgrade gmock/gtest packages.)

BUG=chromium:211445
TEST=build tests for package using gtest 1.6

Change-Id: I1f8cd7a5b9a6f5bcc462ad745667c886fcd6be4c
Reviewed-on: https://gerrit.chromium.org/gerrit/46422
Reviewed-by: Darin Petkov <petkov@chromium.org>
Commit-Queue: Gaurav Shah <gauravsh@chromium.org>
Tested-by: Gaurav Shah <gauravsh@chromium.org>
1 file changed