use Ninja to build grpc_csharp_ext windows artifact

tools/run_tests/artifacts/artifact_targets.py

@@ -240,11 +240,10 @@ class CSharpExtArtifact:
                 ['tools/run_tests/artifacts/build_artifact_csharp_ios.sh'],
                 use_workspace=True)
         elif self.platform == 'windows':
-            cmake_arch_option = 'Win32' if self.arch == 'x86' else self.arch
             return create_jobspec(
                 self.name, [
                     'tools\\run_tests\\artifacts\\build_artifact_csharp.bat',
-                    cmake_arch_option
+                    self.arch
                 ],
                 use_workspace=True)
         else:

tools/run_tests/artifacts/build_artifact_csharp.bat

@@ -15,16 +15,33 @@
 @rem Builds C# artifacts on Windows
 
 set ARCHITECTURE=%1
-set GRPC_SKIP_DOTNET_RESTORE=true
-@call tools\run_tests\helper_scripts\pre_build_csharp.bat %ARCHITECTURE% || goto :error
 
-cd cmake\build\%ARCHITECTURE%
-cmake --build . --target grpc_csharp_ext --config RelWithDebInfo
+@rem enter repo root
+cd /d %~dp0\..\..\..
+
+mkdir cmake
+cd cmake
+mkdir build
+cd build
+mkdir %ARCHITECTURE%
+cd %ARCHITECTURE%
+
+@rem TODO(jtattermusch): is there a better way to force using MSVC?
+@rem select the MSVC compiler explicitly to avoid using gcc from mingw or cygwin
+@rem (both are on path)
+set "MSVC_COMPILER=C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/cl.exe"
+if "%ARCHITECTURE%" == "x64" (
+  set "MSVC_COMPILER=C:/Program Files (x86)/Microsoft Visual Studio 14.0/VC/bin/amd64/cl.exe"
+)
+
+call "%VS140COMNTOOLS%..\..\VC\vcvarsall.bat" %ARCHITECTURE%
+cmake -G Ninja -DCMAKE_C_COMPILER="%MSVC_COMPILER%" -DCMAKE_CXX_COMPILER="%MSVC_COMPILER%" -DCMAKE_BUILD_TYPE=RelWithDebInfo -DgRPC_BUILD_TESTS=OFF -DgRPC_MSVC_STATIC_RUNTIME=ON ../../.. || goto :error
+cmake --build . --target grpc_csharp_ext
 cd ..\..\..
 
 mkdir -p %ARTIFACTS_OUT%
-copy /Y cmake\build\Win32\RelWithDebInfo\grpc_csharp_ext.dll %ARTIFACTS_OUT% || copy /Y cmake\build\x64\RelWithDebInfo\grpc_csharp_ext.dll %ARTIFACTS_OUT% || goto :error
-copy /Y cmake\build\Win32\RelWithDebInfo\grpc_csharp_ext.pdb %ARTIFACTS_OUT% || copy /Y cmake\build\x64\RelWithDebInfo\grpc_csharp_ext.pdb %ARTIFACTS_OUT% || goto :error
+copy /Y cmake\build\%ARCHITECTURE%\grpc_csharp_ext.dll %ARTIFACTS_OUT% || goto :error
+copy /Y cmake\build\%ARCHITECTURE%\grpc_csharp_ext.pdb %ARTIFACTS_OUT% || goto :error
 
 goto :EOF
 

tools/run_tests/helper_scripts/pre_build_csharp.bat

@@ -32,9 +32,7 @@ cmake -G "Visual Studio 14 2015" -A %ARCHITECTURE% -DgRPC_BUILD_TESTS=OFF -DgRPC
 
 cd ..\..\..\src\csharp
 
-if NOT DEFINED GRPC_SKIP_DOTNET_RESTORE (
-  dotnet restore Grpc.sln || goto :error
-)
+dotnet restore Grpc.sln || goto :error
 
 endlocal