Use set() over list() for user_exported_functions. NFC (#13974)

This should always have been a set.  Its never iterated
only ever used for membership check.

Also fix typo in tests/test_other.py.

Split out from #13949

Author: sbc100

emcc.py

@@ -1329,7 +1329,7 @@ def add_link_flag(i, f):
       settings.EXIT_RUNTIME = settings.EXPECT_MAIN
 
     # Note the exports the user requested
-    building.user_requested_exports = settings.EXPORTED_FUNCTIONS.copy()
+    building.user_requested_exports.update(settings.EXPORTED_FUNCTIONS)
 
     def default_setting(name, new_default):
       if name not in settings_map:
@@ -1729,8 +1729,8 @@ def default_setting(name, new_default):
       # kept alive through DCE.
       # TODO: Find a less hacky way to do this, perhaps by also scanning worker.js
       # for roots.
-      building.user_requested_exports.append('_emscripten_tls_init')
-      building.user_requested_exports.append('_emscripten_current_thread_process_queued_calls')
+      building.user_requested_exports.add('_emscripten_tls_init')
+      building.user_requested_exports.add('_emscripten_current_thread_process_queued_calls')
 
       # set location of worker.js
       settings.PTHREAD_WORKER_FILE = unsuffixed(os.path.basename(target)) + '.worker.js'
@@ -1767,7 +1767,7 @@ def default_setting(name, new_default):
       settings.EXPORTED_FUNCTIONS += ['_memalign']
 
       if settings.MINIMAL_RUNTIME:
-        building.user_requested_exports += ['exit']
+        building.user_requested_exports.add('exit')
 
       if settings.PROXY_TO_PTHREAD:
         settings.EXPORTED_FUNCTIONS += ['_emscripten_proxy_main']

emscripten.py

@@ -797,7 +797,7 @@ def load_metadata_wasm(metadata_raw, DEBUG):
   unexpected_exports = [e for e in metadata['exports'] if treat_as_user_function(e)]
   unexpected_exports = [asmjs_mangle(e) for e in unexpected_exports]
   unexpected_exports = [e for e in unexpected_exports if e not in settings.EXPORTED_FUNCTIONS]
-  building.user_requested_exports += unexpected_exports
+  building.user_requested_exports.update(unexpected_exports)
 
   return metadata
 

tests/test_other.py

@@ -10350,9 +10350,9 @@ def test_main_module_no_undefined(self):
     self.run_js('a.out.js')
 
   @parameterized({
-    'main_module': ('-sRELOCATABLE',),
+    'relocatable': ('-sRELOCATABLE',),
     'linkable': ('-sLINKABLE',),
-    'relocatable': ('-sMAIN_MODULE',),
+    'main_module': ('-sMAIN_MODULE',),
   })
   def test_check_undefined(self, flag):
     # positive case: no undefined symbols

tools/building.py

@@ -45,7 +45,7 @@
 ar_contents = {}
 _is_ar_cache = {}
 # the exports the user requested
-user_requested_exports = []
+user_requested_exports = set()
 
 
 class ObjectFileInfo: