[modules] Introduce new VariableLocation for module imports/exports.

src/full-codegen/arm64/full-codegen-arm64.cc

Index: src/full-codegen/arm64/full-codegen-arm64.cc
diff --git a/src/full-codegen/arm64/full-codegen-arm64.cc b/src/full-codegen/arm64/full-codegen-arm64.cc
index 2603d981ab574b9596ccfd7ca1417f337ff90e38..440bac1b071f1a1f7897aee00750dfd6f6639341 100644
--- a/src/full-codegen/arm64/full-codegen-arm64.cc
+++ b/src/full-codegen/arm64/full-codegen-arm64.cc
@@ -804,6 +804,9 @@ void FullCodeGenerator::VisitVariableDeclaration(
       PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
       break;
     }
+
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }
 
@@ -863,6 +866,9 @@ void FullCodeGenerator::VisitFunctionDeclaration(
       PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
       break;
     }
+
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }
 
@@ -1343,6 +1349,9 @@ void FullCodeGenerator::EmitVariableLoad(VariableProxy* proxy,
       context()->Plug(x0);
       break;
     }
+
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }