utils.py: Add a new extend_deps() to easily merge two dependency lists

Add a new extend_deps function to more easily merge two dependency lists.
This avoids adding duplicates, unless the value of the dependency is
different.

Signed-off-by: Mark Hatle <mhatle@windriver.com>

bitbake/lib/bb/utils.py

@@ -287,6 +287,17 @@ def join_deps(deps):
             result.append(dep)
     return ", ".join(result)
 
+def extend_deps(dest, src):
+    """
+    Extend the results from explode_dep_versions by appending all of the items
+    in the second list, avoiding duplicates.
+    """
+    for dep in src:
+        if dep not in dest:
+            dest[dep] = src[dep]
+        elif dest[dep] != src[dep]:
+            dest[dep] = src[dep]
+
 def _print_trace(body, line):
     """
     Print the Environment of a Text Body