fix emscripten dependencies by making separate test crate

lib/emscripten-tests/emtests/test_exceptions_white_list.cpp

@@ -0,0 +1,26 @@
+// Copyright 2016 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>
+
+void thrower() {
+  printf("infunc...");
+  throw(99);
+  printf("FAIL");
+}
+
+void somefunction() {
+  try {
+    thrower();
+  }
+  catch (...) {
+    printf("done!*\n");
+  }
+}
+
+int main() {
+  somefunction();
+  return 0;
+}