* gnu/packages/music.scm (qmmp): Add inputs to support unpacking skins.
[inputs]: Add tar and unzip.
[arguments]: Add phase to set absolute paths to these programs.
Change-Id: I79a6530ad27b474ecc64e5b7de36e0370595bc69
Signed-off-by: Zheng Junjie <zhengjunjie@iscas.ac.cn>