scripts/functions: extract: portable call for old and defective tars

Instead of using -J, --lzma, --use-compress-program or the like
use <compressor> -dc <file> | tar -f -

Signed-off-by: Titus von Boxberg <titus@v9g.de>

 #!/bin/sh

 tail -n+5 "${0}" |bzcat

 exit 0