Change SIMD flags to support aarch64

[KeisukeShima]

Related tier4#8, we changed to not use the architecture-specific SIMD flags in order to support both x64 and aarch64 CPUs.
To accomplish this, we used the -march=native option. According to our internal evaluation, this will specify the best option for each CPU architecture.

[koide3]

I agree that -march=native would be beneficial in many cases. Meanwhile, it sometimes causes segfaults when we build the package with PCL installed via apt. To keep the package usable with the standard prebuilt PCL, I would like to make the march=native flag optional. Could you please update the code so the flag is enabled only when a cmake option is enabled (e.g., -DBUILD_WITH_MARCH_NATIVE=ON)?

[KeisukeShima]

Thanks for your comment. I added a flags to switch the build flags. 57c119c
cc: @harihitode