Store the container annotation in the "containers" directory

Like the OBS worker does.

osc/build.py

@@ -203,6 +203,8 @@ def __init__(self, filename, apiurl, buildtype='spec', localpkgs=None, binarytyp
         else:
             self.preinstallimage = None
 
+        self.containerannotation = root.findtext("containerannotation")
+
     def has_dep(self, name):
         for i in self.deps:
             if i.name == name:
@@ -1320,6 +1322,12 @@ def __str__(self):
                         print("Using prefered package: " + path + "/" + filename)
                         os.unlink(tffn)
 
+        if bi.containerannotation:
+            if not os.path.exists("containers"):
+                os.makedirs("containers")
+            with open("containers/annotation", "wb") as f:
+                f.write(bi.containerannotation.encode())
+
         if prefer_pkgs:
             localpkgdir = "repos/_local/"
             os.mkdir(localpkgdir)