github action - update submodules

.github/workflows/build.yml

@@ -18,6 +18,9 @@ jobs:
         sudo pip install wheel
         sudo pip install cpp-coveralls
     - uses: actions/checkout@v2
+    - name: 'update submodules'
+      run: |
+        git submodule update --init external/rapidjson
     - name: 'build and make'
       run: |
         mkdir build
@@ -35,6 +38,9 @@ jobs:
     runs-on: macos-latest
     steps:
     - uses: actions/checkout@v2
+    - name: 'update submodules'
+      run: |
+        git submodule update --init external/rapidjson
     - name: 'build and make'
       run: |
         mkdir build
@@ -54,7 +60,8 @@ jobs:
     - uses: actions/checkout@v2
     - name: 'update submodules'
       run: |
-        git submodule update --init --recursive
+        git submodule update --init external/rapidjson
+        git submodule update --init external/ios-cmake
     - name: 'build and make'
       run: |
         mkdir build && cd build
@@ -81,6 +88,9 @@ jobs:
     runs-on: windows-latest
     steps:
     - uses: actions/checkout@v2
+    - name: 'update submodules'
+      run: |
+        git submodule update --init external/rapidjson
     - name: 'add msbuild'
       uses: microsoft/setup-msbuild@v1.0.2
     - name: 'build and make'