ci: fix windows paths

Author: adil192

.github/shared_workflows/setup_flutter/action.yml

@@ -4,20 +4,21 @@ description: "Setup Flutter and caches"
 runs:
   using: "composite"
   steps:
-    - name: Add Flutter to PATH
+    - name: Add env variables
       shell: bash
       run: |
-        echo "${{ github.workspace }}/submodules/flutter/bin" >> $GITHUB_PATH
-        echo "${{ github.workspace }}/submodules/flutter/.pub-cache/bin" >> $GITHUB_PATH
+        WORKSPACE=${{ runner.os == 'Windows' && echo "${GITHUB_WORKSPACE//\\//}" || echo "${GITHUB_WORKSPACE}" }}
+        echo "FLUTTER_ROOT=${WORKSPACE}/submodules/flutter" >> $GITHUB_ENV
+        echo "PUB_CACHE=${WORKSPACE}/submodules/flutter/.pub-cache" >> $GITHUB_ENV
+        ENGINE_VERSION=$(cat ${WORKSPACE}/submodules/flutter/bin/internal/engine.version)
+        FLUTTER_PACKAGES_VERSION=$(cat ${WORKSPACE}/submodules/flutter/bin/internal/flutter_packages.version)
+        echo "FLUTTER_HASH=${ENGINE_VERSION}-${FLUTTER_PACKAGES_VERSION}" >> $GITHUB_ENV
 
-    - name: Add env variables
+    - name: Add Flutter to PATH
       shell: bash
       run: |
-        echo "FLUTTER_ROOT=${{ github.workspace }}/submodules/flutter" >> $GITHUB_ENV
-        echo "PUB_CACHE=${{ github.workspace }}/submodules/flutter/.pub-cache" >> $GITHUB_ENV
-        ENGINE_VERSION=$(cat ${{ github.workspace }}/submodules/flutter/bin/internal/engine.version)
-        FLUTTER_PACKAGES_VERSION=$(cat ${{ github.workspace }}/submodules/flutter/bin/internal/flutter_packages.version)
-        echo "FLUTTER_HASH=${ENGINE_VERSION}-${FLUTTER_PACKAGES_VERSION}" >> $GITHUB_ENV
+        echo "${{ env.FLUTTER_ROOT }}/bin" >> $GITHUB_PATH
+        echo "${{ env.PUB_CACHE }}/bin" >> $GITHUB_PATH
 
     - name: Cache Flutter
       id: cache-flutter