Previously we modify the CLI options store to indicate whether the
isolate is created for building snapshot, which is a bit hacky and
makes it difficult to tell whether the snapshot is built from the
command line or through other APIs. This patch adds
is_building_snapshot to IsolateData and use this instead when we
need to know whether the isolate is created for building snapshot
(but do not care about where that request is coming from).

This patch adds a new ERR_NOT_SUPPORTED_IN_SNAPSHOT error and throw
it in the worker constructor.

…operation

Co-authored-by: Anna Henningsen <[email protected]>