Add support for Linux aarch64 architecture (ARM)

[markphip]

This adds support for building on Linux aarch64

I was specifically testing in Docker on MacOS with Apple Silicon. I tested with Debian and Ubuntu base images.

• HEN_HOUSE/scripts/config.guess: Added a new case for aarch64 in the Linux environment to return the machine type as aarch64-unknown-linux-gnu.
• HEN_HOUSE/scripts/configure: Set the memory_model to an empty string if the canonical_system is aarch64.
• HEN_HOUSE/scripts/configure_c++: Set the memory_model to an empty string if the canonical_system is aarch64. Also, added a new case for aarch64 in the Linux environment to set the fpic flag to -fPIC and add -Wno-narrowing to opt. [1] [2]