`autoclean.c` build error in master

[grubles]

Master at 4b69c57d75e78cb5aa91bb3554925bb610759fe9 errors when building autoclean.c on OpenBSD 7.5 with clang.

$ cc --version
OpenBSD clang version 16.0.6
Target: amd64-unknown-openbsd7.5

cc plugins/autoclean.c
plugins/autoclean.c:260:7: error: format specifies type 'unsigned long long' but the argument has type 'size_t' (aka 'unsigned long') [-Werror,-Wformat]
                           num_cleaned, subsystem_to_str(&sv));
                           ^~~~~~~~~~~
1 error generated.
gmake: *** [Makefile:301: plugins/autoclean.o] Error 1