Allow conditional builds of grpc_csharp_ext for vcpkg manager

templates/CMakeLists.txt.template

@@ -87,6 +87,7 @@
   # Options
   option(gRPC_BUILD_TESTS "Build tests" OFF)
   option(gRPC_BUILD_CODEGEN "Build codegen" ON)
+  option(gRPC_BUILD_CSHARP_EXT "Build C# extensions" ON)
 
   set(gRPC_INSTALL_default ON)
   if (NOT CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
@@ -298,6 +299,11 @@
   if (gRPC_BUILD_TESTS)
   ${cc_library(lib)}
   endif (gRPC_BUILD_TESTS)
+  % elif lib.name in ['grpc_csharp_ext']:
+  if (gRPC_BUILD_CSHARP_EXT)
+  ${cc_library(lib)}
+  ${cc_install(lib)}
+  endif (gRPC_BUILD_CSHARP_EXT)
   % else:
   ${cc_library(lib)}
   % if not lib.build in ["tool"]: