make runtime compatible with wasm

runtime/internal/lib/internal/goarch/goarch_wasm.go

@@ -0,0 +1,13 @@
+// Copyright 2018 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package goarch
+
+const (
+	_ArchFamily          = WASM
+	_DefaultPhysPageSize = 65536
+	_PCQuantum           = 1
+	_MinFrameSize        = 0
+	_StackAlign          = PtrSize
+)