Also print the exception when mksnapshot failed to compile extra code.

Before, it would only print the exception when it failed to run the code

R=svenpanne@chromium.org

Review URL: https://codereview.chromium.org/14031036

Patch from Jochen Eisinger <jochen@chromium.org>.

git-svn-id: https://v8.googlecode.com/svn/branches/bleeding_edge@14478 ce2b1a6d-e550-0410-aec6-3dcde31c8c00