Support disabling vendored OpenSSL while building

[orhun]

Hey, I'm the maintainer of the monolith package for Arch Linux 👋

I saw that in the latest version OpenSSL is being linked statically, which is something that I wanted to avoid for the package. I was able to do it by using OPENSSL_NO_VENDOR=1 flag but thought it would be better to add a feature flag for it so that I can do --no-default-features next time :)

Cheers!

[snshn]

Hey Orhun,

thank you for maintaining the Arch package and making this PR!

OpenSSL is a real pain in the neck to deal with, I'm currently trying to find the best combination of solutions to make everyone happy, and it's tricky due to dealing with cross-platform issues and different architectures.

I'll go ahead and merge this PR for it to be available in the next release, it may be useful for other package maintainers and users as well. I may have to ditch static linking if it creates any more issues, it's more of an experiment, and I hope it was a step in the right direction (many people were having issues with the binary not finding their library).