The `CacheStream::commit()` function (defined in Caching.cpp) deletes
the underlying raw stream. Some output streamers may hold a pointer
to it, which then will outlive the stream object.
In particular, MCAsmStreamer keeps the pointer to the raw stream
though a separate `formatted_raw_stream` object, which buffers data and
there is no path to explicitly flush this data. Before this change,
the buffered data was flushed during the MCAsmStreamer destructor.
After #136121, this happened after the `commit()` function is called.
Therefore, it caused a crash because the `formatted_raw_stream` object
tries to write the buffered data into a deleted raw stream. Even if
we don't delete the stream to avoid the crash, it would be too late
as the output stream cannot accept data after commit().
Fixes: #138194.
eac7466448