Currently, nosnap builds do not run mksnapshot and thus do not have a
chance to generate the embedded blob. In theory we could support this,
but let's just ensure we don't crash for now.

Bug: v8:6666,v8:7835
Change-Id: I7d3b1f772b296ae3bcaed1604e0d1e44834da1c0
Reviewed-on: https://chromium-review.googlesource.com/1092491Reviewed-by: Tobias Tebbi <tebbi@chromium.org>
Commit-Queue: Jakob Gruber <jgruber@chromium.org>
Cr-Commit-Position: refs/heads/master@{#53600}