misc/mbuffer: Update 20250429 => 20250809

20250809:

• Fix CMake build issue
• Fix some warnings on intentionally ignored return values

• Use https:// URI scheme for MASTER_SITES
• Remove GNU_CONFIGURE_MANPREFIX (already set by default in Mk/bsd.port.mk:2697)
• Pet portclippy(1) and portfmt(1)

PR: 289897
Submitted by: alven, takefu@airport.fm