Bug 1063880 - Do not emit Linkable-derived objects when COMPILE_ENVIRONMENT is not set. r=mshal

python/mozbuild/mozbuild/frontend/emitter.py

@@ -161,11 +161,14 @@ class TreeMetadataEmitter(LoggingMixin):
             else:
                 raise Exception('Unhandled output type: %s' % type(out))
 
-        start = time.time()
-        objs = list(self._emit_libs_derived(contexts))
-        emitter_time += time.time() - start
+        # Don't emit Linkable objects when COMPILE_ENVIRONMENT is explicitely
+        # set to a value meaning false (usually '').
+        if self.config.substs.get('COMPILE_ENVIRONMENT', True):
+            start = time.time()
+            objs = list(self._emit_libs_derived(contexts))
+            emitter_time += time.time() - start
 
-        for o in emit_objs(objs): yield o
+            for o in emit_objs(objs): yield o
 
         yield ReaderSummary(file_count, sandbox_execution_time, emitter_time)