bitbake: data/siggen: Switch md5 -> sha256

Similarly to the codeparser change, change to sha256 hashes due to worries
over collisions. The main impact of this change is slightly slower parsing
time as well as longer sstate file names.

(Bitbake rev: 66f1b766997d53b4375fdd25719b1175f3828903)

Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>

bitbake/lib/bb/data_smart.py

@@ -1074,4 +1074,4 @@ class DataSmart(MutableMapping):
                     data.update({i:value})
 
         data_str = str([(k, data[k]) for k in sorted(data.keys())])
-        return hashlib.md5(data_str.encode("utf-8")).hexdigest()
+        return hashlib.sha256(data_str.encode("utf-8")).hexdigest()