Fix version dep8 test on riscv64

autopkgtests don't pass in debian CI for riscv64, as the version test tries to run peekfd, which is not built for that architecture. This changeset checks for the architecture before trying to execute peekfd so the test passes there.

When checking this I saw the manpage for peekfd is present in riscv64 systems, and that doesn't really make sense as the binary is not present. As there is already a rule to exclude the manpage on specific situations, I've changed it to exclude it anywhere it's not built (similar to the logic applied to fuser in the lines above.