bug#29700: Java packages need to retain references

[Ricardo Wurmus <rekado@elephly.net>]

Hi Gábor,

The manifest file would not be sufficient.  Take the example of
“java-usb4java”.  It provides a file “share/java/usb4java.jar”, which
contains this manifest:

--8<---------------cut here---------------start------------->8---
Manifest-Version: 1.0
Created-By: 1.7.0_161 (Oracle Corporation)

--8<---------------cut here---------------end--------------->8---

When you open the Loader.class file that is included in the archive you
will notice that it contains this string:

    /gnu/store/iwjqaqr98daqbgwswqi5fi4w891bqh7d-libusb4java-0-1.396d642a5/lib/libusb4java.so

This reference is currently dropped because it cannot be detected in a
compressed archive.  The reference is not contained in the manifest, and
at build time we could only guess which references should be added to
the manifest.

Unless we extend the reference scanner to deal with compressed files I
think that disabling compression in jars is the best approach.

I’ll push this to master.

--
Ricardo

GPG: BCA6 89B6 3655 3801 C3C6  2150 197A 5888 235F ACAC
https://elephly.net