sl: add .hash file
Fixes:
http://autobuild.buildroot.org/results/22e/22e78cfb88f2fc6f6f8b7a0afafbb5eb101bb982/
Similar to jquery-keyboard, it seems the sl tarball on the autobuilder is
corrupt. Fix it by adding a .hash file so it falls back to our s.b.o
mirror.
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>
Peter Korsgaard