fix win RBE opt build

tools/bazel.rc

@@ -12,6 +12,9 @@ build:opt --copt=-Wframe-larger-than=16384
 
 build:dbg --compilation_mode=dbg
 
+build:windows_opt --compilation_mode=opt
+build:windows_dbg --compilation_mode=dbg
+
 build:asan --strip=never
 build:asan --copt=-fsanitize=address
 build:asan --copt=-O0

tools/internal_ci/windows/grpc_bazel_rbe_dbg.cfg

@@ -34,8 +34,7 @@ bazel_setting {
 env_vars {
   # flags will be passed to bazel invocation by bazel_rbe.bat
   key: "BAZEL_FLAGS"
-  # TODO(jtattermusch): add --config=dbg once that works
-  value: "--cache_test_results=no"
+  value: "--cache_test_results=no --config=windows_dbg"
 }
 
 env_vars {

tools/internal_ci/windows/grpc_bazel_rbe_opt.cfg

@@ -34,7 +34,7 @@ bazel_setting {
 env_vars {
   # flags will be passed to bazel invocation by bazel_rbe.bat
   key: "BAZEL_FLAGS"
-  value: "--cache_test_results=no --config=opt"
+  value: "--cache_test_results=no --config=windows_opt"
 }
 env_vars {
   key: "UPLOAD_TEST_RESULTS"

tools/internal_ci/windows/pull_request/grpc_bazel_rbe_dbg.cfg

@@ -34,6 +34,5 @@ bazel_setting {
 env_vars {
   # flags will be passed to bazel invocation by bazel_rbe.bat
   key: "BAZEL_FLAGS"
-  # TODO(jtattermusch): add --config=dbg once that works
-  value: ""
+  value: " --config=windows_dbg"
 }

tools/internal_ci/windows/pull_request/grpc_bazel_rbe_opt.cfg

@@ -34,5 +34,5 @@ bazel_setting {
 env_vars {
   # flags will be passed to bazel invocation by bazel_rbe.bat
   key: "BAZEL_FLAGS"
-  value: "--config=opt"
+  value: "--config=windows_opt"
 }

tools/remote_build/windows.bazelrc

@@ -1,5 +1,9 @@
 startup --host_jvm_args=-Dbazel.DigestFunction=SHA256
 
+# TODO(jtattermusch): Currently building with --compilation_mode=dbg is broken on Windows RBE
+# so we need to explicitly override it to use fastbuild.
+build:windows_dbg --compilation_mode=fastbuild
+
 build --remote_cache=grpcs://remotebuildexecution.googleapis.com
 build --remote_executor=grpcs://remotebuildexecution.googleapis.com