Add some minimal testing against jsc (javascriptcore) (#19626)

This should allow me to write a test for #18357 that can run in
CI without requiring us to setup a full safari test environment.

Author: sbc100

.circleci/config.yml

@@ -580,6 +580,28 @@ jobs:
           title: "wasm64"
           test_targets: "wasm64 wasm64l.test_bigswitch"
       - upload-test-results
+  test-jsc:
+    executor: linux-python
+    steps:
+      - checkout
+      - run:
+          name: submodule update
+          command: git submodule update --init
+      - pip-install
+      - build
+      - run:
+          name: install jsc
+          command: |
+            cd $HOME
+            wget https://nodejs.org/dist/v18.12.0/node-v18.12.0-linux-x64.tar.xz
+            tar -xf node-v18.12.0-linux-x64.tar.xz
+            export PATH="`pwd`/node-v18.12.0-linux-x64/bin:${PATH}"
+            npm install jsvu -g
+            jsvu --os=default --engines=javascriptcore
+            echo "JSC_ENGINE = [os.path.expanduser('~/.jsvu/bin/javascriptcore')]" >> ~/emsdk/.emscripten
+            echo "JS_ENGINES = [JSC_ENGINE]" >> ~/emsdk/.emscripten
+      - run-tests:
+          test_targets: "core0.test_hello_world"
   test-node-compat:
     # We don't use `bionic` here since its tool old to run recent node versions:
     # `/lib/x86_64-linux-gnu/libc.so.6: version `GLIBC_2.28' not found`
@@ -788,6 +810,7 @@ workflows:
       - test-sockets-chrome:
           requires:
             - build-linux
+      - test-jsc
       - test-node-compat
       - test-windows
       - test-mac-arm64

test/common.py

@@ -685,6 +685,11 @@ def setUp(self):
     self.required_engine = None
     self.wasm_engines = config.WASM_ENGINES.copy()
     self.use_all_engines = EMTEST_ALL_ENGINES
+    if self.js_engines[0] != config.NODE_JS:
+      # If our primary JS engine is something other than node then enable
+      # shell support.
+      default_envs = 'web,webview,worker,node'
+      self.set_setting('ENVIRONMENT', default_envs + ',shell')
 
     if EMTEST_DETECT_TEMPFILE_LEAKS:
       for root, dirnames, filenames in os.walk(self.temp_dir):
@@ -1981,7 +1986,7 @@ def btest(self, filename, expected=None, reference=None,
     if not isinstance(expected, list):
       expected = [expected]
     if EMTEST_BROWSER == 'node':
-      self.js_engines = [config.NODE_JS]
+      self.require_node()
       self.node_args += shared.node_pthread_flags()
       output = self.run_js('test.js')
       self.assertContained('RESULT: ' + expected[0], output)