Isolated emscripten in new lib

lib/emscripten/emtests/test_em_asm_unicode.cpp

@@ -0,0 +1,10 @@
+// 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 <emscripten.h>
+
+int main() {
+  EM_ASM( out("hello world…") );
+}