makepkg: always keep sources symlinks
Make bunzip2/xz/gunzip decompressing to stdout, because gzip does not offer
something like a -k option.
The selection of the decompression command for gzip/bzip2/xz compressed
files now also depends on the file suffix, since we need to strip the
extensions to get the output filename.
Thanks to Cedric Staniewski <cedric@gmx.ca> for reporting this issue and
contributing patches.
Signed-off-by: Xavier Chantry <shiningxc@gmail.com>
Signed-off-by: Dan McGee <dan@archlinux.org>