package/qdecoder: add .hash file

Similar to jquery-keyboard, it seems the qdecoder 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: Romain Naour <romain.naour@gmail.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>

package/qdecoder/qdecoder.hash

@@ -0,0 +1,2 @@
+# Locally calculated
+sha256 641d3df4895626d7a530c5d26724e9b5887e9845d4b47f42c1cbce4a17ebf6af  qdecoder-r12.0.5.tar.gz