Pass property arguments as custom_var values.

This passes property arguments passed to the recipe as custom_var values.

This allows the DEPS file respond to command line parameters from the
'fetch' command.

b/70641101

Change-Id: I68c73dd77c18adf860976fc4ae6be42b8675f1b7
diff --git a/recipes/cobalt.py b/recipes/cobalt.py
index dc9f77f..0de554e 100644
--- a/recipes/cobalt.py
+++ b/recipes/cobalt.py
@@ -26,6 +26,7 @@
                  'managed'   : True,
                  'custom_deps': {},
                  'safesync_url': '',
+                 'custom_vars': props,
     }
     spec = {
       'solutions': [solution],