[wasm] Separate compilation from instantiation

test/unittests/wasm/ast-decoder-unittest.cc

Index: test/unittests/wasm/ast-decoder-unittest.cc
diff --git a/test/unittests/wasm/ast-decoder-unittest.cc b/test/unittests/wasm/ast-decoder-unittest.cc
index 55c7095f80f506e31333a721d1ee7d6a5a4edd8d..8be0e414afed97a7683c0281c45ca7d609815d27 100644
--- a/test/unittests/wasm/ast-decoder-unittest.cc
+++ b/test/unittests/wasm/ast-decoder-unittest.cc
@@ -1156,7 +1156,6 @@ class TestModuleEnv : public ModuleEnv {
   TestModuleEnv() {
     instance = nullptr;
     module = &mod;
-    linker = nullptr;
   }
   byte AddGlobal(MachineType mem_type) {
     mod.globals.push_back({0, 0, mem_type, 0, false});