Do not list file names during 'cmake -E tar xz'

Since commit "Switch to using libarchive from libtar" (2009-10-30) the
the implementation of "tar xz" has printed all paths from the tarball as
a single line with no separator.  This fixes the logic to extract
silently as expected.

Source/cmSystemTools.cxx

@@ -2048,12 +2048,13 @@ bool extract_tar(const char* outFileName, bool verbose,
     if (verbose && extract)
       {
       cmSystemTools::Stdout("x ");
+      cmSystemTools::Stdout(archive_entry_pathname(entry));
       }
     if(verbose && !extract)
       {
       list_item_verbose(stdout, entry);
       }
-    else
+    else if(!extract)
       {
       cmSystemTools::Stdout(archive_entry_pathname(entry));
       }