fix emscripten dependencies by making separate test crate

lib/emscripten-tests/emtests/test_direct_string_constant_usage.c

@@ -0,0 +1,16 @@
+/*
+ * 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 <iostream>
+template <int i>
+void printText(const char (&text)[i]) {
+  std::cout << text;
+}
+int main() {
+  printText("some string constant");
+  return 0;
+}