Build failed to compile on Raspberry Pi 4, with
clang: error: the clang compiler does not support '-march=native'
The build script checks $OS_ARCH for `arm64` to distinghuish between ARM
and X64 architecture. However on Raspberry Pi, the `uname -m` command
reports `aarch64` rather than `arm64`.
This change updates the EXTRAFLAGS of the `release-native` target to
check for both - `arm64` and `aarch64`.
