Update out-of-date RELEASE instructions (#9505)

Author: elliette

tool/RELEASE_INSTRUCTIONS.md

@@ -160,18 +160,27 @@ Receive an LGTM for the PR, squash and commit.
 
 ### 5) Wait for the binary to be uploaded CIPD
 
-On each DevTools commit, DevTools is built and uploaded to CIPD. You can check the
-status of the builds on this
+On each DevTools commit, DevTools is built and uploaded to CIPD. You can check
+the status of the builds on this
 [dashboard](https://ci.chromium.org/ui/p/dart-internal/builders/flutter/devtools).
-Within minutes, a build should be uploaded for the commit you just merged and tagged.
+Within minutes, a build should be uploaded for the commit you just merged and
+tagged.
 
-> [!NOTE]  
-> If the CIPD build times out, instructions for re-triggering can be found at
-[go/dart-engprod/release.md](http://go/dart-engprod/release.md)
+If you don't see a build, you can check the following yourself or ask a Googler
+to check them for you:
+
+1. Check the source mirror:
+   [go/flutter-devtools-sourcemirror](http://go/flutter-devtools-sourcemirror).
+   The CIPD build can only begin once the commit is reflected in the source
+   mirror. 
+2. If you see the commit in the source mirror, but the the CIPD build times out,
+instructions for re-triggering can be found at
+[go/devtools-dart-engprod#cherry-picks](http://go/devtools-dart-engprod#cherry-picks).
+**Note: Use `refs/heads/master` as the branch.**
 
 ### 6) Update the DevTools hash in the Dart SDK
 
-Run the tool script with the commit hash you just merged and tagged:
+Run the tool script with the commit hash you just merged:
 ```shell
 dt update-sdk-deps -c <commit-hash>
 ```
@@ -184,15 +193,20 @@ Quickly test the build and then add a reviewer:
    ```shell
    cd $LOCAL_DART_SDK && \
    gclient sync -D && \
-   ./tools/build.py -mrelease -ax64 create_sdk;
+   ./tools/build.py -mrelease create_sdk;
    ```
 
 2. Verify that running `dart devtools` launches the version of DevTools you just released.
-   - for OSX
+   - for Macs with ARM-based processors (M chips):
+      ```shell
+      xcodebuild/ReleaseARM64/dart-sdk/bin/dart devtools
+      ```
+   - for Macs with x64-based processors (Intel chips):
       ```shell
       xcodebuild/ReleaseX64/dart-sdk/bin/dart devtools
       ```
-   - For non-OSX
+
+   - For non-Macs:
       ```shell
       out/ReleaseX64/dart-sdk/bin/dart devtools
       ```
@@ -416,13 +430,22 @@ onto the `flutter/devtools` protected branch (`master`).
 
    Body:
 
-   > 1\. Temporarily modify the settings of https://github.com/flutter/devtools to "allow merge
-   >    commits at the repo level and remove `require linear history`".\
+   > 1\. Temporarily modify the settings of https://github.com/flutter/devtools to allow merge
+   >     commits at the repo level and remove require linear history for the master branch:
+   > 
+   > 1a. General > Pull Requests > Allow merge commits (Add all commits from the head branch 
+   >     to the base branch with a merge commit).
+   > 
+   > 1b. Branches > Branch protection rules > click “edit” on the master branch > Remove >
+   >     Require linear history (Prevent merge commits from being pushed to matching branches),
+   >     and then “Save changes”.
+   > 
    > 2\. IMPORTANT: Merge <link to PR> as a MERGE COMMIT. When merging, use the merge button dropdown
-   >    menu to select "Create a merge commit", NOT "Squash and merge".\
+   >     menu to select "Create a merge commit", NOT "Squash and merge".
+   >
    > 3\. Revert the settings.
 
-    If @kenzieschmoll is unavailable to complete the merge commit, please ask another member of the Dash
+    If @kenzieschmoll or @elliette is unavailable to complete the merge commit, please ask another member of the Dash
     team who has Admin access to the `flutter/devtools` repository settings (@piinks or @tvolkert).
 
 ### Additional resources