chore(CI): Split Win deps into their own job

Previously, the four matrix Windows jobs would run in parallel and each
build deps, which is redundant since both debug and release qTox use the
same deps.

Now, the win-deps job builds only the needed two versions of deps, and
the four windows builds wait for it to complete before running in
parallel.

.github/workflows/test.yaml

@@ -70,16 +70,14 @@ jobs:
       - uses: actions/checkout@v2
       - name: Run
         run: ./flatpak/build-flatpak.sh
-  win:
-    name: Windows
+  win-deps:
+    name: Windows Deps
     runs-on: ubuntu-latest
     strategy:
       matrix:
         arch: [i686, x86_64]
-        type: [debug, release]
     env:
       BUILD__: ${{ matrix.arch }}
-      BTYPE__: ${{ matrix.type }}
     steps:
       - uses: actions/checkout@v2
       - name: Cache dependencies
@@ -98,6 +96,24 @@ jobs:
         run: |
           ./.travis/build-windows.sh "$BUILD__" "release" "cache/${BUILD__}" stage2
           ls -al cache
+  win:
+    name: Windows
+    runs-on: ubuntu-latest
+    needs: win-deps
+    strategy:
+      matrix:
+        arch: [i686, x86_64]
+        type: [debug, release]
+    env:
+      BUILD__: ${{ matrix.arch }}
+      BTYPE__: ${{ matrix.type }}
+    steps:
+      - uses: actions/checkout@v2
+      - name: Fetch cached dependencies
+        uses: actions/cache@v2
+        with:
+          path: cache
+          key: deps-${{ matrix.arch }}-${{ hashFiles('windows/cross-compile/build.sh') }}-${{ hashFiles('.travis/build-windows.sh') }}
       - name: qTox build
         run: |
           ./.travis/build-windows.sh "$BUILD__" "$BTYPE__" "cache/${BUILD__}" stage3