Unlike COPTS=-DHAVE_DNSSEC, allow usage of just sha256 function from
nettle, but keep DNSSEC disabled at build time. Skips use of internal
hash implementation without support for validation built-in.
If arg2 of pkg-wrapper is "--copy", then arg1 is NOT the name of
the package manager (--copy doesn't invoke it) it's a secondary
config string that inhibts the copy if found. This patch allows that
to be the empty string, for unconditional copy, and modifies the
ubus linker config to use it. It worked by coincidence before, because
there was no config string called "pkg-config".
