Create more reproducible .zip files

[bmwiedemann]

While working on reproducible builds for openSUSE, I found that
the fs-uae.dat in our package varied for every build.

Therefore I propose this patch to
Create more reproducible .zip files
avoid indeterministic filesystem order
and use -X to omit extended attributes from zip file
to help make fs-uae package build reproducible

See https://reproducible-builds.org/ for why this is good.

One remaining issue is with mtimes that also get embedded into the zip.

touch -d@$CONSTANT can help there (but only with GNU touch).

or touch -r $REFERENCEFILE (works with GNU touch and BSD touch)

or we post-process it in our package build process with strip-nondeterminism -t zip

[FrodeSolheim]

Looks good, thanks :)