Enable CGO

This ensures Full RELRO[1] and helps build on riscv64[2].

[1] https://wiki.archlinux.org/title/Go_package_guidelines#Flags_and_build_options

[2] Build on riscv64 fails with:

==> Starting build()...
-buildmode=pie requires external (cgo) linking, but cgo is not enabled
==> ERROR: A failure occurred in build().