* gnu/packages/patches/unzip-CVE-2014-9636.patch,
  gnu/packages/patches/unzip-allow-greater-hostver-values.patch,
  gnu/packages/patches/unzip-increase-size-of-cfactorstr.patch,
  gnu/packages/patches/unzip-initialize-symlink-flag.patch,
  gnu/packages/patches/unzip-remove-build-date.patch: New files.
* gnu-system.am (dist_patch_DATA): Add them.
* gnu/packages/zip.scm (unzip)[source]: Add patches.
  [arguments]: Use 'modify-phases'.  Remove custom 'configure' phase; pass
  additional make-flags instead.  Add custom 'build' phase that builds
  "generic_gcc" target; remove "generic_gcc" from make-flags.