Update Centos7 action to use an absolute path for RESINSIGHT_GRPC_PYTHON_EXECUTABLE

.github/workflows/centos7.yml

@@ -38,20 +38,24 @@ jobs:
       uses: actions/checkout@v2
       with:
         submodules: true
-          
+    - name: Set up Python
+      id: python-path
+      run: |
+        source /opt/rh/rh-python36/enable
+        python -c "import sys; print(sys.version)"
+        run: echo "::set-output name=PYTHON_EXECUTABLE::$(python -c 'import sys; import pathlib; print (pathlib.PurePath(sys.executable).as_posix())')"
     - name: Build ResInsight
       run: |
-        
         source /opt/rh/devtoolset-7/enable
         source /opt/rh/rh-python36/enable
 
         cmake3 --version
         git --version
         g++ --version
-        python --version
+        ${{ steps.python-path.outputs.PYTHON_EXECUTABLE }} --version
 
-        python -m pip install --upgrade pip
-        python -m pip install grpcio-tools
+        ${{ steps.python-path.outputs.PYTHON_EXECUTABLE }} -m pip install --upgrade pip
+        ${{ steps.python-path.outputs.PYTHON_EXECUTABLE }} -m pip install grpcio-tools
 
         ThirdParty/vcpkg/bootstrap-vcpkg.sh 
         ThirdParty/vcpkg/vcpkg install grpc boost-filesystem eigen3
@@ -64,7 +68,7 @@ jobs:
         -DRESINSIGHT_ENABLE_UNITY_BUILD=true \
         -DVCPKG_TARGET_TRIPLET=x64-linux \
         -DCMAKE_TOOLCHAIN_FILE=../ThirdParty/vcpkg/scripts/buildsystems/vcpkg.cmake \
-        -DRESINSIGHT_GRPC_PYTHON_EXECUTABLE=python \
+        -DRESINSIGHT_GRPC_PYTHON_EXECUTABLE=${{ steps.python-path.outputs.PYTHON_EXECUTABLE }} \
         -DRESINSIGHT_GRPC_DOWNLOAD_PYTHON_MODULE=true \
         ..