Add feature vendored-engine for engine support in openssl-src

[neuronull]

NOTE this change depends on the following PR being merged into openssl-src : alexcrichton/openssl-src-rs#150 , and thus CI will fail until that is made available. Posting this PR in anticipation of that for visibility.

One of our project dependency crates added a hard dependency on the openssl Engine module.

This created a problem when cross compiling with musl due to the disabling of the Engine module by openssl-src for the musl target.

By adding the option to enable Engine support in openssl-src , and adding this feature flag to openssl-sys to make use of that option, together this would unblock us .

[sfackler]

It seems like it would be better for this to be modeled as a Cargo feature in openssl-src like all of the other configuration.

[jszwedko]

@sfackler Agreed this should be a feature flag on openssl-src. Once that is added, we will need a new in openssl-sys to enable the flag on openssl-src though, right? Would you be open to that?

I.e. something like:

[features]
vendored = ['openssl-src']
+ vendored-engine = ['openssl-src/engine']

[neuronull]

I submitted a new PR to openssl-src for the feature flag (alexcrichton/openssl-src-rs#151)

New PR because I needed to change to the 111 release.

[sfackler]

@jszwedko you don't need that:

[dependencies]
openssl = { version = "0.10", features = ["vendored"] }

[build-dependencies]
openssl-src = { version = "111", features = ["engine"] }

[neuronull]

This was covered in alexcrichton/openssl-src-rs#151.

Closing