- add direct dependant settings
- only compile mksnapshot on the host toolset

BUG=none
LOG=n
R=machenbach@chromium.org, brettw@chromium.org

Review URL: https://codereview.chromium.org/314073002

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@21689 ce2b1a6d-e550-0410-aec6-3dcde31c8c00