FreeBSD_HEAD_arm64 - Build #3963 - Fixed

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FreeBSD_HEAD_arm64 - Build #3963 - Fixed:

Build information: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD_arm64/3963/
Full change log: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD_arm64/3963/changes
Full build log: https://jenkins.FreeBSD.org/job/FreeBSD_HEAD_arm64/3963/console

Change summaries:

305903 by kib:
Fix libprocstat build after r305902.
- Use _Bool to not require userspace to include stdbool.h.
- Make extattr.h usable without vnode_if.h.
- Follow i_ump to get cdev pointer.

Sponsored by:	The FreeBSD Foundation
MFC after:	2 weeks