Adds xtensa arch to build script

[StefanB7]

Adds the xtensa arch to the build script.

The expressif micro controllers use xtensa chips + architecture, that doesn't have 64 bit support. The esp-rs organisation has a fork of the rust programming language that includes support for the xtensa architecture. The target in my config.toml file: target = "xtensa-esp32s3-none-elf"

Thanks

[myrrlyn]

Since v1, we use the cfg(target_has_atomic = "width") compiler flags. I am working on migrating bitvec to use v1 instead of v0, but this can be forced by applying

[patch.crates-io]
radium = "1.0" # or "1.1"

in your manifest.

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I've tried installing the ESP-RS toolchain on my machine to check if radium compiles with it. I haven't been able to get it to work yet but I'm also only about two hours in. Would you be willing to clone ferrilab/ferrilab (I am archiving the individual repositories, since a single workspace makes development much easier going forward) and check if radium works as expected on the XTensa targets?