Only look for an app snapshot embedded in a dynamic library in the AOT runtime.
Only look for an app snapshot embedded in a dynamic library in the AOT runtime.

This mode is only intended for simulating iOS for testing. User-facing app snapshots only use regular files.

Avoids an error message on Fuchsia.

R=zra@google.com

Review-Url: https://codereview.chromium.org/2646733004 .

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