Build ASan-instrumented and multithreaded libraries

Author: quantum5

tools/system_libs.py

@@ -528,11 +528,6 @@ def vary_on(cls):
       vary_on += ['is_asan']
     return vary_on
 
-  @classmethod
-  def variations(cls):
-    return [variation for variation in super(AsanInstrumentedLibrary, cls).variations()
-            if not shared.Settings.WASM_BACKEND or not variation['is_asan'] or not variation.get('is_mt')]
-
   @classmethod
   def get_default_variation(cls, **kwargs):
     return super(AsanInstrumentedLibrary, cls).get_default_variation(is_asan=shared.Settings.USE_ASAN, **kwargs)