fix emscripten dependencies by making separate test crate

lib/emscripten-tests/emtests/test_exceptions_virtual_inheritance.cpp

@@ -0,0 +1,33 @@
+// Copyright 2014 The Emscripten Authors.  All rights reserved.
+// Emscripten is available under two separate licenses, the MIT license and the
+// University of Illinois/NCSA Open Source License.  Both these licenses can be
+// found in the LICENSE file.
+
+#include <iostream>
+#include <stdexcept>
+
+using std::cout;
+using std::endl;
+
+struct my_exception : public virtual std::runtime_error {
+  // To allow this to be thrown directly in the tests below.
+  explicit my_exception(const std::string &what)
+    : std::runtime_error(what)
+  {}
+
+protected:
+    my_exception()
+      // This won't be called because of virtual inheritance.
+      : std::runtime_error("::my_exception")
+  {}
+};
+
+int main(const int argc, const char * const * const argv) {
+  try {
+    cout << "Throwing ::my_exception" << endl;
+    throw ::my_exception("my_what");
+  } catch(const std::runtime_error &ex) {
+    cout << "Caught std::runtime_error: " << ex.what() << endl;
+  }
+}
+