Add extract-native-libraries-from-jars? option

[AdamClements]

This searches uberjars on the classpath for /native/linux//.so native android libraries and includes those libraries in the build, according to the file layout at https://github.com/swannodette/native-deps.

Should not affect existing native-libs handling at all but offers an alternative to package native binaries with jars for android.

Current issues:

• It's a bit slow - adds half a second on my current classpath. Could do with some way of realising it's already checked jars and only refreshing on a change.
• Copying happens on every build, again, could do with a method to determine that the file is already extracted and skip
• Probably not in the right place/namespace, should happen a little earlier in the process and simply add its directory to the normal native-libraries-paths vector.

If you want to suggest/review any changes I'd be happy to tweak a little more.

[alexander-yakushev]

Hello Adam,

I'm all for adding this feature. As for the issues: a) extra 0.5 seconds is OK to sacrifice; b) figuring out a caching mechanism to avoid copies every time is enough trouble to just let it copy; c) for the namespace you are right, it doesn't seem to fit into sdk completely. Could you separate all utility functions into a new namespace (something like native.clj or anything better you might think of)?

Also can you please trim the code to fit into 80 chars per line? I try to honour this limit.

Finally, it would be a good idea to eventually add the boilerplate to Leiningen itself, if this way of locating libs is standard. I may try to ask on the #leiningen list.

[AdamClements]

Okay, I have rejigged it into its own namespace and added a cache in the target folder so it'll get blown away with a lein clean. The cache looks at full path of the jar to say whether its dealt with it before and if it has, skips the copy step as well as the jar scanning step, this drops the whole cost to 0.5seconds on the first run and negligible thereafter.

The only edge case I can think of is that you might need to clean between snapshots if your snapshot has updated... don't know what it chooses for snapshot paths, if there's a unique part of the file name then that's not even a problem.

Now it has caching, I wonder if this should be on by default and do away with the option? Your call.

[alexander-yakushev]

All the rest seems OK as long as it works.

One more thing. After you make the final changes, could you please squash all suggested commits into one? To avoid creating abother pull request you can do git rewrite -i on your branch, squash the commits and then forcefully push with git push -f.

[alexander-yakushev]

Hey, Phil just told me there is leiningen.core.classpath/extract-native-deps function that should do the same job. Can we leverage that instead?

[AdamClements]

Oh. Yeah, that'd be much easier, all we actually need to do is add target/native/linux to the native-dependencies vector if it exists... Sort of annoying but ah well! I might just delete this pull request, start again.