fix emscripten dependencies by making separate test crate

lib/emscripten-tests/emtests/test_exceptions_multiple_inherit.cpp

@@ -0,0 +1,31 @@
+// Copyright 2018 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 <stdio.h>
+#include <exception>
+
+// multiple inheritance of base classes that are not empty, so adjustments are necessary
+
+struct boost_exception {
+  int x;
+};
+
+struct my_error: boost_exception, std::exception { };
+
+int main() {
+  try {
+    throw my_error();
+  } catch( boost_exception & ) {
+    puts("a");
+    try {
+      puts("b");
+      throw;
+     } catch( my_error & ) {
+        puts("c");
+     }
+  }
+  puts("d");
+  return 0;
+}