security/certmgr: fix build on riscv64

• bump golang.org/x/sys dependency to 0.5.0 to add missing riscv64-freebsd bits
• remove lots of useless GH_TUPLE entries (these are already vendored in the upstream repository).
• move REINPLACE_CMD to pre-configure to simplify make makepatch

Tested by: dmgk
Approved by: flo (mentor)
Sponsored by: Berliner Linux User Group e.V.
Differential Revision: https://reviews.freebsd.org/D38684