Disabling the use of pulumi watch on darwin/arm64 architecture (#6497)

CHANGELOG_PENDING.md

@@ -15,7 +15,8 @@
 - [build] Updating Pulumi to use Go 1.16
   [#6470](https://github.com/pulumi/pulumi/pull/6470)
 
-- [build] Adding a Pulumi arm64 binary for use on new macOS hardware
+- [build] Adding a Pulumi arm64 binary for use on new macOS hardware.  
+  Please note that `pulumi watch` will not be supported on darwin/arm64 builds.
   [#6492](https://github.com/pulumi/pulumi/pull/6492)
 
 ### Bug Fixes

pkg/backend/watch.go

@@ -1,3 +1,5 @@
+// +build !darwin !arm64
+
 // Copyright 2016-2019, Pulumi Corporation.
 //
 // Licensed under the Apache License, Version 2.0 (the "License");

pkg/backend/watch_darwin_arm64.go

@@ -0,0 +1,26 @@
+// Copyright 2016-2019, Pulumi Corporation.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package backend
+
+import (
+	"context"
+	"errors"
+
+	"github.com/pulumi/pulumi/sdk/v2/go/common/util/result"
+)
+
+func Watch(ctx context.Context, b Backend, stack Stack, op UpdateOperation, apply Applier) result.Result {
+	return result.FromError(errors.New("pulumi watch is not currently supported on darwin/arm64"))
+}