Pin Windows builds to Dart 2.4

See dart-lang/sdk#38334

.travis.yml

@@ -64,6 +64,9 @@ jobs:
     env: DART_CHANNEL=dev
   - <<: *dart-tests
     os: windows
+    # File system watching is extra flaky on Dart 2.5.0 on Windows (see
+    # dart-lang/sdk#38334).
+    env: DART_VERSION=2.4.1
   - <<: *dart-tests
     os: osx
 
@@ -110,10 +113,12 @@ jobs:
       (type IN (push, api)) AND (repo = sass/dart-sass) AND tag =~ ^\d+\.\d+\.\d+([+-].*)?$
     script: pub run grinder sanity-check-before-release
 
-  # Deploy Linux and Windows releases to GitHub. Mac OS releases are deployed in
-  # a later stage so that we can build application snapshots on Mac OS bots.
+  # Deploy Linux releases to GitHub. Mac OS releases are deployed in a later
+  # stage so that we can build application snapshots on Mac OS bots, and Windows
+  # releases are deployed later so they can use Dart 2.4.1 to work around
+  # dart-lang/sdk#38334.
   - stage: deploy 1
-    name: "GitHub: Windows and Linux"
+    name: "GitHub: Linux"
     if: *deploy-if
     env: &github-env
       - GITHUB_USER=sassbot
@@ -125,7 +130,7 @@ jobs:
     script: skip # Don't run tests
     deploy:
       provider: script
-      script: pub run grinder github-release github-linux github-windows
+      script: pub run grinder github-release github-linux
       skip_cleanup: true # Don't clean up the Dart SDK.
 
       # This causes the deploy to only be build when a tag is pushed. This
@@ -183,6 +188,9 @@ jobs:
   - name: Chocolatey
     if: *deploy-if
     env:
+      # File system watching is extra flaky on Dart 2.5.0 on Windows (see
+      # dart-lang/sdk#38334).
+      - DART_VERSION=2.4.1
       # CHOCO_TOKEN="..."
       - secure: "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"
     script: skip
@@ -232,3 +240,26 @@ jobs:
       script: pub run grinder github-mac-os
       skip_cleanup: true
       on: {tags: true}
+
+  - name: "GitHub: Windows"
+    if: *deploy-if
+    env:
+      # We can't re-use the github-env alias here because we also need to
+      # override DART_VERSION.
+      #
+      # File system watching is extra flaky on Dart 2.5.0 on Windows (see
+      # dart-lang/sdk#38334).
+      - DART_VERSION=2.4.1
+      - GITHUB_USER=sassbot
+      # GITHUB_AUTH="..."
+      #
+      # Note that this overrides the read-only auth token that's set for all
+      # builds.
+      - secure: "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"
+
+    script: skip
+    deploy:
+      provider: script
+      script: pub run grinder github-windows
+      skip_cleanup: true
+      on: {tags: true}