remove -mfpu=neon for aarch64

[mchalain]

The neon fpu is mandatory for aarch64, and GCC doesn't recognize this option.

Tested with Raspberry Pi 4 64bits

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[Copilot]

Pull Request Overview

This PR removes the GCC unsupported "-mfpu=neon" flag for aarch64 builds by updating the CMake logic.

• Removed the condition that set ARCH_BIT to "-mfpu=neon".
• Now, when no experimental features are enabled, ARCH_BIT is set to "-m64", relying on aarch64’s mandatory neon FPU.

Comments suppressed due to low confidence (1)

cmake_utils/CMake_linux_tools.cmake:31

• When any of EXPERIMENTAL_USE_VENUM, OPENVX_USE_TILING, or EXPERIMENTAL_USE_OPENCL are enabled, ARCH_BIT is left unset. Please confirm that this behavior is intentional and that a default value is not required for these cases.

if (NOT EXPERIMENTAL_USE_VENUM AND NOT OPENVX_USE_TILING AND NOT EXPERIMENTAL_USE_OPENCL)

[simonCatBot]

Review: Build Fix for aarch64

This is a straightforward and necessary fix. The NEON flag is indeed not recognized on aarch64 since NEON is mandatory on ARM64 architecture.

Assessment: LGTM - Ready to merge.

The change properly removes the flag conditionally while preserving it for 32-bit ARM builds where it is still needed. Tested on Raspberry Pi 4 64-bit as noted. Simple, low-risk fix that improves build portability.