fix emscripten dependencies by making separate test crate

lib/emscripten-tests/emtests/stackAlloc.cpp

@@ -0,0 +1,35 @@
+// 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({
+    var size = 128;
+    var before;
+    before = stackSave();
+    var x = stackAlloc(size);
+    var y = stackAlloc(size);
+    var direction = y > x ? 1 : -1;
+    assert(x % 16 == 0, "allocation must have 16-byte alignment");
+    assert(x == Math.min(before, before + direction*size), "allocation must return the start of the range allocated");
+    var z = stackAlloc(size);
+    assert(x != y && y != z && x != z, "allocations must be unique");
+    assert((y - x)*(z - y) > 0, "allocations must be in the same direction");
+    // no overlaps
+    function notInRange(value, begin, end) {
+      function errormsg() { return value + " must not be in the range (" + begin + ", " + end + "]"; }
+      if (begin < end) assert(!(value >= begin && value < end), errormsg());
+      else assert(!(value <= begin && value > end), errormsg());
+    }
+    notInRange(x, y, y + direction*size);
+    notInRange(x, z, z + direction*size);
+    notInRange(y, x, x + direction*size);
+    notInRange(y, z, z + direction*size);
+    notInRange(z, x, x + direction*size);
+    notInRange(z, y, y + direction*size);
+    out('ok.');
+  });
+}