chore: enable platform-specific configs and silence C++ warnings in .bazelrc (#3738)

Silence spammy C++ compile warnings in build logs to make it easier
to identify actual issues. The warnings were primarily deprecation
notices from external dependencies (like protobuf) observed during
both target and tool compilation.

Platform-specific configurations were enabled because C++ compiler flags
(copts) differ significantly for Windows (which typically uses MSVC)
compared to Linux and macOS (which use GCC/Clang). Applying the warning-
silencing flags globally would break Windows builds. This approach
allows us to safely ignore these specific warnings only on platforms
where the flags are supported.

Author: rickeylev

.bazelrc

@@ -25,6 +25,9 @@ common --incompatible_disallow_struct_provider_syntax
 # Makes Bazel 7 act more like Bazel 8
 common --incompatible_use_plus_in_repo_names
 
+# Implicitly adds --config=linux|macos|windows, depending on the host platform
+common --enable_platform_specific_config
+
 # Needed to make Windows with a py_binary in data deps work. The Bazel launcher
 # is used, which falls back to finding python.exe on PATH to bootstrap.
 # See https://github.com/bazel-contrib/rules_python/issues/3655
@@ -55,6 +58,20 @@ common --incompatible_no_implicit_file_export
 
 build --lockfile_mode=update
 
+# Silence spammy C++ compile warnings
+build:linux --copt=-Wno-deprecated-declarations
+build:linux --copt=-Wno-stringop-overread
+build:linux --copt=-Wno-sign-compare
+build:linux --host_copt=-Wno-deprecated-declarations
+build:linux --host_copt=-Wno-stringop-overread
+build:linux --host_copt=-Wno-sign-compare
+build:macos --copt=-Wno-deprecated-declarations
+build:macos --copt=-Wno-stringop-overread
+build:macos --copt=-Wno-sign-compare
+build:macos --host_copt=-Wno-deprecated-declarations
+build:macos --host_copt=-Wno-stringop-overread
+build:macos --host_copt=-Wno-sign-compare
+
 import %workspace%/specialized_configs.bazelrc
 
 try-import user.bazelrc