package/axel: fix link order

libintl may use thread-related functions, so -lpthread must come after
-lintl.

Fixes:
    http://autobuild.buildroot.org/results/e9d/e9d89fd5b24a76a3c5ab9dc8f01f4643f7c13396/



[Peter: use -lpthread in comment as suggested by Arnout]
Signed-off-by: "Yann E. MORIN" <yann.morin.1998@free.fr>
Reviewed-by: Arnout Vandecappelle (Essensium/Mind) <arnout@mind.be>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>