Remove test platform specification from release config

#test-continuous

PiperOrigin-RevId: 731139639

.github/workflows/test_cpp.yml

@@ -52,7 +52,7 @@ jobs:
             cache_key: TcMalloc
             image: "us-docker.pkg.dev/protobuf-build/containers/test/linux/tcmalloc:7.1.2-d9624f2aa83cba3eaf906f751d75b36aacb9aa82"
             targets: "//src/... //third_party/utf8_range/..."
-          - config: { name: "aarch64" }
+          - config: { name: "aarch64", flags: "--platforms=//build_defs:aarch64_linux" }
             cache_key: aarch64-bazel7
             targets: "//src/... //src/google/protobuf/compiler:protoc_aarch64_test //third_party/utf8_range/..."
             image: "us-docker.pkg.dev/protobuf-build/containers/test/linux/emulation:7.1.2-aarch64-2920199ab0090ed427413a8e422e62695c8392a8"

toolchain/toolchains.bazelrc

@@ -3,9 +3,8 @@ build:cross_config --//toolchain:release=true
 build:cross_config --host_crosstool_top=@bazel_tools//tools/cpp:toolchain
 build:cross_config --incompatible_enable_cc_toolchain_resolution=false
 
-# Set platform explicitly for aarch64 emulation images.
-build:linux-aarch_64 --config=cross_config --cpu=linux-aarch_64 --platforms=//build_defs:aarch64_linux
-build:linux-aarch64 --config=cross_config --cpu=linux-aarch_64 --platforms=//build_defs:aarch64_linux
+build:linux-aarch_64 --config=cross_config --cpu=linux-aarch_64
+build:linux-aarch64 --config=cross_config --cpu=linux-aarch_64
 build:linux-ppcle_64 --config=cross_config --cpu=linux-ppcle_64
 build:linux-ppc64le --config=cross_config --cpu=linux-ppcle_64
 build:linux-s390_64 --config=cross_config --cpu=linux-s390_64