Fix is-check for avxvnniint8 #320

Job	Run time
build-and-test / cmake-linux-aarch64	4m 30s
build-and-test / cmake-linux-riscv64-rvv	17m 57s
build-and-test / cmake-linux-x86_64	1m 22s
build-and-test / cmake-linux-riscv64	2m 54s
build-and-test / cmake-windows-arm64	2m 59s
build-and-test / cmake-windows-x64	5m 42s
build-and-test / bazel-linux-x86_64-clang-18	4m 17s
build-and-test / bazel-linux-x86_64-gcc-9	3m 19s
build-and-test / bazel-linux-aarch64	1m 35s
build-and-test / cmake-android (arm64)	1m 44s
build-and-test / cmake-android (armv7)	1m 40s
build-and-test / cmake-ios-arm64	4m 8s
build-and-test / cmake-android (x86)	2m 0s
build-and-test / cmake-ios-x86_64	6m 5s
build-and-test / cmake-linux-armhf	2m 10s
build-and-test / cmake-macos-arm64	7m 30s
build-and-test / cmake-windows-x86	7m 27s
	1h 17m 19s

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