Enable libcpp hardening by default in public fleetbench, as Google has enabled libcpp hardening throughout its production environments.

PiperOrigin-RevId: 741199261
Change-Id: I385760f051df85eb8cc5e13402d01ea812e4ef58

Author: Fleetbench Team

.bazelrc

@@ -26,6 +26,9 @@ build --@com_github_grpc_grpc//:disable_grpc_rls
 build --define=grpc_no_xds=true
 test --test_timeout=1500
 
+# Enable bounds-checking assertions in LLVM libcpp containers by default.
+build --copt='-D_LIBCPP_HARDENING_MODE=_LIBCPP_HARDENING_MODE_FAST'
+
 # Define the --config=asan-libfuzzer configuration.
 build:asan-libfuzzer --@rules_fuzzing//fuzzing:cc_engine=@rules_fuzzing//fuzzing/engines:libfuzzer
 build:asan-libfuzzer --@rules_fuzzing//fuzzing:cc_engine_instrumentation=libfuzzer
@@ -75,4 +78,4 @@ build:westmere --copt='-mpclmul'
 build:westmere --copt='-mprefer-vector-width=128'
 build:westmere --copt='-msse4.2'
 
-build:arm --copt='-mtune=generic'
+build:arm --copt='-mtune=generic'