Disable -Wnullability-completeness on iOS and macOS. (#782)

* Disable -Wnullability-completeness on iOS and macOS.

* Remove NDK if the cache hit failed.

Author: jonsimantov

.github/workflows/android.yml

@@ -91,6 +91,17 @@ jobs:
           path: /tmp/android-ndk-r16b
           key: android-ndk-${{ matrix.os }}-r16b
 
+      - name: Check cached NDK
+        shell: bash
+        if: steps.cache_ndk.outputs.cache-hit != 'true'
+        run: |
+          # If the NDK failed to download from the cache, but there is a
+          # /tmp/android-ndk-r16b directory, it's incomplete, so remove it.
+          if [[ -d "/tmp/android-ndk-r16b" ]]; then
+            echo "Removing incomplete download of NDK"
+            rm -rf /tmp/android-ndk-r16b
+          fi
+
       - name: Update homebrew (avoid bintray errors)
         uses: nick-invision/retry@v2
         if: startsWith(matrix.os, 'macos')

CMakeLists.txt

@@ -147,6 +147,13 @@ if(DESKTOP AND APPLE)
   endif()
 endif()
 
+if(APPLE)
+  # For iOS and macOS, disable nullability completeness warning, as it makes the
+  # build output for our Objective-C++ files much too verbose.
+  set(CMAKE_C_FLAGS "${CMAKE_C_FLAGS} -Wno-nullability-completeness")
+  set(CMAKE_CXX_FLAGS "${CMAKE_CXX_FLAGS} -Wno-nullability-completeness")
+endif()
+
 if(DESKTOP AND NOT MSVC AND NOT APPLE)
   # Linux-specific option.
   if (FIREBASE_LINUX_USE_CXX11_ABI)