bug#29700: Java packages need to retain references

[Ricardo Wurmus]

I installed the “axoloti-patcher” package today after “guix gc” and
noticed that not all dependencies are available at runtime.  Upon
running the “Axoloti” command I got this error:

    Exception in thread "AWT-EventQueue-0" java.lang.UnsatisfiedLinkError: 
Can't load library: 
/gnu/store/nrx5nmwynmsl7aqxdpgwpsm8ff9b0h4d-libusb4java-0-1.396d642a5/lib/libusb4java.so

The store item does not exist.

The problem here is that jar archives are compressed and thus any
references they contain are thus hidden from the scanner.

I don’t know if it is feasible to disable compression for jar files, or
if we should install a “.guix-dependencies” file that contains plain
text references.

I’ll investigate disabling compression first.  Looks like we can do this
in the strip-jar-timestamps phase where we use “zip” to repack the jar.
Adding “-0” to the arguments should be enough to make this work.

I’ll send a patch soon.

--
Ricardo

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