Remove obscure uses of shell redirections.
    
    This patch makes the spec file slightly more friendly to non-shell
    readers by changing "> foo" to "truncate -s 0 foo" and removes
    the use of ">> foo". The use of ">> foo" is perhaps the most
    interesting shell trick which is used to create a zero sized
    debuginfocommon.filelist, but only if it doesn't already exist.
    This allows the subsequent command to use debuginfocommon.filelist
    without requiring it be wrapped in a check for
    %{debuginfocommonarches}. That seems a little obtuse and certainly
    confusing to the reader who expects such a check for anything
    that is related to the debuginfo common package.