Upgrade gdbstub to 0.6.4 am: 925e9a2e74 am: fda7e1bf84 am: c0a7518181

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

Change-Id: I60e6387a6aaba813787de817d932c98e138c592e
Signed-off-by: Automerger Merge Worker <[email protected]>