Bug 1227892 - Add a NO_COMPONENTS_MANIFEST moz.build variable. r=gps

The variable is used by Lightning in comm-central and influences
binary-component manifest creation.

python/mozbuild/mozbuild/frontend/context.py

@@ -1717,6 +1717,11 @@ VARIABLES = {
         """Forces to build a real static library, and no corresponding fake
            library.
         """, None),
+
+    'NO_COMPONENTS_MANIFEST': (bool, bool,
+        """Do not create a binary-component manifest entry for the
+        corresponding XPCOMBinaryComponent.
+        """, None),
 }
 
 # Sanity check: we don't want any variable above to have a list as storage type.

python/mozbuild/mozbuild/frontend/emitter.py

@@ -582,6 +582,7 @@ class TreeMetadataEmitter(LoggingMixin):
             'LD_VERSION_SCRIPT',
             'USE_EXTENSION_MANIFEST',
             'NO_JS_MANIFEST',
+            'NO_COMPONENTS_MANIFEST',
         ]
         for v in varlist:
             if v in context and context[v]: