ci: upgrade flutter version on windows arm (#1269)

.github/workflows/build.yml

@@ -44,15 +44,17 @@ jobs:
           - arch: arm64
             os: windows-11-arm
             llvm_ver: "20251202" # Only ARM64
-            flutter_channel: "master"
-            flutter_version: "8817d45220d" # Only ARM64
+            flutter_channel: "main"
+            flutter_version: "7e1c8868"
           - arch: amd64
             os: windows-2022
-            flutter_channel: "stable"
     runs-on: ${{ matrix.os }}
 
     steps:
       - uses: actions/checkout@v3
+      - name: Enable long paths for flutter main branch checks
+        run: |
+          git config --global core.longpaths true
 
       # Install LLVM environment only on ARM64
       - name: Install llvm-mingw-ucrt-aarch64 (ARM64 only)
@@ -84,7 +86,7 @@ jobs:
           go-version: ${{ env.GO_VERSION }}
       - uses: subosito/flutter-action@v2
         with:
-          channel: ${{ matrix.flutter_channel }}
+          channel: ${{ matrix.flutter_channel || 'stable' }}
           flutter-version: ${{ matrix.flutter_version || env.FLUTTER_VERSION }}
       - name: Build
         env: