Set the correct L2 size for Ampere Altra (`aarch64`). #411

Job	Run time
cmake-darwin	28s
cmake-android (android-arm64-build.sh)	1m 38s
cmake-linux-riscv64	6s
cmake-linux-local	37s
cmake-android (android-armv7-build.sh)	2m 36s
cmake-uwp	1m 20s
cmake-android (android-riscv64-build.sh)	51s
cmake-windows	1m 23s
cmake-android (android-x86-build.sh)	1m 4s
	10m 3s

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