Let -s RELOOPER work correctly.

emscripten.py

@@ -1333,6 +1333,8 @@ def main(args, compiler_engine, cache, jcache, relooper, temp_files, DEBUG, DEBU
 
   # Compile the assembly to Javascript.
   if settings.get('RELOOP'):
+    if not relooper:
+      relooper = settings.get('RELOOPER')
       if not relooper:
         relooper = cache.get_path('relooper.js')
     settings.setdefault('RELOOPER', relooper)

tools/shared.py

@@ -1417,6 +1417,7 @@ class Building:
     os.environ['EMSCRIPTEN_SUPPRESS_USAGE_WARNING'] = '1'
 
     # Run Emscripten
+    if not os.path.exists(Settings.RELOOPER):
       Settings.RELOOPER = Cache.get_path('relooper.js')
     settings = Settings.serialize()
     args = settings + extra_args