fix emscripten dependencies by making separate test crate

lib/emscripten-tests/emtests/test_emscripten_api.cpp

@@ -0,0 +1,43 @@
+// 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 <assert.h>
+#include <limits.h>
+#include <stdio.h>
+#include "emscripten.h"
+
+extern "C" {
+void save_me_aimee() { printf("mann\n"); }
+}
+
+int main() {
+  // EMSCRIPTEN_COMMENT("hello from the source");
+  emscripten_run_script("out('hello world' + '!')");
+  printf("*%d*\n", emscripten_run_script_int("5*20"));
+  printf("*%s*\n", emscripten_run_script_string("'five'+'six'"));
+  emscripten_run_script("Module['_save_me_aimee']()");
+  //
+  double d = 0.1234567891231219886553;
+  int len = emscripten_print_double(d, NULL, -1);
+  char buffer[len+1];
+  buffer[len] = CHAR_MAX;
+  emscripten_print_double(d, buffer, len+1);
+  assert(buffer[len] == 0); // null terminated
+  double e;
+  sscanf(buffer, "%lf", &e);
+  printf("%.30lf : %s : %.30lf  (%d)\n", d, buffer, e, len);
+
+  buffer[0] = 1;
+  buffer[1] = 2;
+  buffer[2] = 3;
+  int n = emscripten_print_double(d, buffer, 2);
+  assert(n == 1);
+  assert(buffer[0] == '0'); // touched
+  assert(buffer[1] == 0); // touched
+  assert(buffer[2] == 3); // untouched
+  puts("success\n");
+
+  return 0;
+}