Consider switching out OpenSSL for Rustls

[TobiasDeBruijn]

Hi,

Thanks for the hard work!

Just an idea, would it be worth it to switch out OpenSSL for Rustls? This would allow for easier portable binaries among other features. reqwest can easily be made to use rustls rather than native-tls (i.e openssl) by disabling the default features and enabling the rustls-tls feature.

I noticed that sccache also directly depends on Openssl, but I have not checked how and why.

Thanks!

[drahnr]

There has been an effort in #879 #272 to achieve this and it works just fine in https://github.com/paritytech/cachepot where this is already included in master