explorercanvas: add .hash file
Fixes:
http://autobuild.buildroot.org/results/51c/51ca42d031814e7d6650701ea285cb7e1f31bcea/
http://autobuild.buildroot.org/results/dc5/dc55e5f210c90dbaa4bb051bf489c53c18462828/
Similar to jquery-keyboard, it seems the explorercanvas 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