See https://codeberg.org/op/gmid/issues/2

so that we don't have to hardcode /etc in gmid.c. Helps on systems like FreeBSD where the non-base programs are expected to look for their config in /usr/local/etc.

this time targetting ABI level 3; partially based on how claudio@ handled it in rpki-client. Fun how this bit of code has come full circle (gmid inspired what I wrote for got, which inspired what was written for rpki-client, which has come back.)

on macos we have the situation where we have arc4random available but no getentropy().

gmid (like all other daemons that want to do privsep crypto) has a very close relationship with libtls and need to stay in sync with it. OpenBSD' libtls was recently changed to use OpenSSL' EC_KEY_METHOD instead of the older ECDSA_METHOD, on the gmid side we have to do the same otherwise failures happens at runtime. In a similar manner, privsep crypto is silently broken in the current libretls (next version should fix it.) The proper solution would be to complete the signer APIs so that applications don't need to dive into the library' internals, but that's a mid-term goal, for the immediate bundling the 'little' libtls is the lesser evil. The configure script has gained a new (undocumented for the time being) flag `--with-libtls=bundled|system' to control which libtls to use. It defaults to `bundled' except for OpenBSD where it uses the `system' one. Note that OpenBSD versions before 7.3 (inclusive) ought to use --with-libtls=bundled too since they still do ECDSA_METHOD.