Make a copy of the argument File's FileHeader, and pass a pointer
to the copy to CreateRaw.
Passing the pointer directly causes the entire `File` to be referenced
by the receiver. The `File` includes a reference to the `ReaderAt`
underlying the `Reader`, so all its memory, which may be the entire
contents of the archive, is prevented from being garbage-collected.
Also, explain the issue in the doc comment for CreateRaw. We
cannot change its behavior because someone may depend on the
preserving the identity of its argument pointer.
For #65499.
Change-Id: Ieb4963a0ea30539d597547d3511accbd8c6b5c5a
Reviewed-on: https://go-review.googlesource.com/c/go/+/560238
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com> Reviewed-by: Damien Neil <dneil@google.com>