[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 096c0358a029a1acf742d2a23d9c84e506fd45ca..8af038adc8a26c70c590b4fc181f75428d0fd9a4 100644
--- a/src/full-codegen/arm64/full-codegen-arm64.cc
+++ b/src/full-codegen/arm64/full-codegen-arm64.cc
@@ -799,6 +799,9 @@ void FullCodeGenerator::VisitVariableDeclaration(
       PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
       break;
     }
+
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }
 
@@ -858,6 +861,9 @@ void FullCodeGenerator::VisitFunctionDeclaration(
       PrepareForBailoutForId(proxy->id(), BailoutState::NO_REGISTERS);
       break;
     }
+
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }
 
@@ -1336,6 +1342,9 @@ void FullCodeGenerator::EmitVariableLoad(VariableProxy* proxy,
       context()->Plug(x0);
       break;
     }
+
+    case VariableLocation::MODULE:
+      UNREACHABLE();
   }
 }