Isolated emscripten in new lib

lib/emscripten/emtests/test_main_module_static_align.cpp

@@ -0,0 +1,18 @@
+// 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>
+
+__attribute__((aligned(16))) volatile char aligned;
+
+int main() {
+  emscripten_log(EM_LOG_WARN, "16-byte aligned char: %d.", int(&aligned));
+  EM_ASM({
+    // whether the char was properly aligned affects tempDoublePtr, which is after the static aligns
+    out('tempDoublePtr: ' + tempDoublePtr + '.');
+    out('tempDoublePtr alignment: ' + (tempDoublePtr % 16) + '.');
+  });
+}
+