pcr: slf4j: add unzip forgotten depdency
    
    Without that fix, it wokrs fine with makepkg but fails with libremakepkg
    with the following error:
     |  ==> Starting prepare()...
     |  /startdir/PKGBUILD: line 141: unzip: command not found
     |  ==> ERROR: A failure occurred in prepare().
     |      Aborting...
    
    Signed-off-by: Denis 'GNUtoo' Carikli <GNUtoo@cyberdimension.org>