Even more BCR Fixes

.bazelrc

@@ -7,8 +7,17 @@ test --sandbox_tmpfs_path=/tmp
 common --java_runtime_version=remotejdk_21
 
 # Set C++ standard to C++17 for abseil-cpp compatibility
-build --cxxopt=-std=c++17
-build --host_cxxopt=-std=c++17
+# Use GCC/Clang flags for Unix-like systems
+build:linux --cxxopt=-std=c++17
+build:linux --host_cxxopt=-std=c++17
+build:macos --cxxopt=-std=c++17
+build:macos --host_cxxopt=-std=c++17
+# Use MSVC flags for Windows
+build:windows --cxxopt=/std:c++17
+build:windows --host_cxxopt=/std:c++17
+
+# Auto-detect platform and apply appropriate config
+build --enable_platform_specific_config
 
 # Avoid cache thrashing, but allow integration tests to find "bazel" on the PATH.
 common --incompatible_strict_action_env

.bcr/presubmit.yml

@@ -36,8 +36,8 @@ tasks:
     platform: windows
     bazel: "7.x"
     build_flags:
-    - '--cxxopt=-std=c++17'
-    - '--host_cxxopt=-std=c++17'
+    - '--cxxopt=/std:c++17'
+    - '--host_cxxopt=/std:c++17'
     build_targets:
     - '@bazel-diff//:bazel-diff'
   verify_targets_windows_8x:
@@ -46,8 +46,8 @@ tasks:
     bazel: "8.x"
     build_flags:
     - '--legacy_external_runfiles'
-    - '--cxxopt=-std=c++17'
-    - '--host_cxxopt=-std=c++17'
+    - '--cxxopt=/std:c++17'
+    - '--host_cxxopt=/std:c++17'
     build_targets:
     - '@bazel-diff//:bazel-diff'
   verify_targets_windows_9x:
@@ -56,8 +56,8 @@ tasks:
     bazel: "9.x"
     build_flags:
     - '--legacy_external_runfiles'
-    - '--cxxopt=-std=c++17'
-    - '--host_cxxopt=-std=c++17'
+    - '--cxxopt=/std:c++17'
+    - '--host_cxxopt=/std:c++17'
     build_targets:
     - '@bazel-diff//:bazel-diff'
 bcr_test_module: