Setup default test settings in test/common.py. NFC (#25083)

Emscripten itself never uses these values.

Author: sbc100

test/common.py

@@ -137,9 +137,14 @@ def configure(data_dir):
 WASM_DIS = os.path.join(building.get_binaryen_bin(), 'wasm-dis')
 LLVM_OBJDUMP = shared.llvm_tool_path('llvm-objdump')
 PYTHON = sys.executable
+
+assert config.NODE_JS # assert for mypy's benefit
+# By default we run the tests in the same version of node as emscripten itself used.
 if not config.NODE_JS_TEST:
   config.NODE_JS_TEST = config.NODE_JS
-
+# The default set of JS_ENGINES contains the just node.
+if not config.JS_ENGINES:
+  config.JS_ENGINES = [config.NODE_JS_TEST]
 
 requires_network = unittest.skipIf(os.getenv('EMTEST_SKIP_NETWORK_TESTS'), 'This test requires network access')
 

tools/config.py

@@ -62,10 +62,6 @@ def normalize_config_settings():
   global CACHE, PORTS, LLVM_ADD_VERSION, CLANG_ADD_VERSION, CLOSURE_COMPILER
   global NODE_JS, NODE_JS_TEST, V8_ENGINE, JS_ENGINES, SPIDERMONKEY_ENGINE, WASM_ENGINES
 
-  # EM_CONFIG stuff
-  if not JS_ENGINES:
-    JS_ENGINES = [NODE_JS_TEST if NODE_JS_TEST else NODE_JS]
-
   SPIDERMONKEY_ENGINE = fix_js_engine(SPIDERMONKEY_ENGINE, listify(SPIDERMONKEY_ENGINE))
   NODE_JS = fix_js_engine(NODE_JS, listify(NODE_JS))
   NODE_JS_TEST = fix_js_engine(NODE_JS_TEST, listify(NODE_JS_TEST))