CI: Install Android NDK r23c explicitly

It has just been removed from the Ubuntu 20.04 default install,
breaking our CI setup.

Author: akien-mga

.github/workflows/ci.yml

@@ -65,7 +65,7 @@ jobs:
             platform: android
             artifact-name: godot-cpp-android-arm64-release
             artifact-path: bin/libgodot-cpp.android.template_release.arm64.a
-            flags: ANDROID_NDK_ROOT=$ANDROID_NDK_LATEST_HOME arch=arm64
+            flags: arch=arm64
             run-tests: false
             cache-name: android-arm64
 
@@ -108,11 +108,12 @@ jobs:
         with:
           python-version: '3.x'
 
-      - name: Linux dependencies
-        if: ${{ matrix.platform == 'linux' }}
-        run: |
-          sudo apt-get update -qq
-          sudo apt-get install -qqq build-essential pkg-config
+      - name: Android dependencies
+        if: ${{ matrix.platform == 'android' }}
+        uses: nttld/setup-ndk@v1
+        with:
+          ndk-version: r23c
+          link-to-sdk: true
 
       - name: Web dependencies
         if: ${{ matrix.platform == 'web' }}
@@ -121,16 +122,16 @@ jobs:
           version: ${{env.EM_VERSION}}
           actions-cache-folder: ${{env.EM_CACHE_FOLDER}}
 
-      - name: Install scons
-        run: |
-          python -m pip install scons==4.0.0
-
       - name: Setup MinGW for Windows/MinGW build
         if: ${{ matrix.platform == 'windows' && matrix.flags == 'use_mingw=yes' }}
         uses: egor-tensin/setup-mingw@v2
         with:
           version: 12.2.0
 
+      - name: Install scons
+        run: |
+          python -m pip install scons==4.0.0
+
       - name: Generate godot-cpp sources only
         run: |
           scons platform=${{ matrix.platform }} build_library=no ${{ matrix.flags }}