Upgrade gdbstub to 0.6.4 am: 925e9a2e74

Original change: https://android-review.googlesource.com/c/platform/external/rust/crates/gdbstub/+/2469443

Change-Id: Ib483e90cc604884b257a4e4d71ffe0a079004c20
Signed-off-by: Automerger Merge Worker <[email protected]>