The `build_odin` flags include the option `release-native`.
The current `EXTRAFLAGS` set however don't work for Arm CPUs as they dont support `-march=native`.
Added code to detect CPU and either set the preferred flag for Arm CPUs (ie `-mcpu=native`) or keep the current default.
Information on preferred Arm CPU optimisation flag taken from here: https://community.arm.com/arm-community-blogs/b/tools-software-ides-blog/posts/compiler-flags-across-architectures-march-mtune-and-mcpu
Changes tested on an Apple Silicon M1 CPU (arm64) using HomeBrew installed llvm as follows:
```
Homebrew clang version 14.0.6
Target: arm64-apple-darwin22.5.0
Thread model: posix
InstalledDir: /opt/homebrew/opt/llvm@14/bin
```
