fix emscripten dependencies by making separate test crate

lib/emscripten-tests/emtests/legacy_exported_runtime_numbers.cpp

@@ -0,0 +1,19 @@
+// Copyright 2017 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<emscripten.h>
+
+int main() {
+#ifdef DIRECT
+  EM_ASM({
+    out('|' + ALLOC_DYNAMIC + '|');
+  });
+#else
+  EM_ASM({
+    out('|' + Module['ALLOC_DYNAMIC'] + '|');
+  });
+#endif
+}
+