====== Cross-compile for Raspberry Pi 4 ======
===== Overview =====
I've found a number of how-tos on the net about cross-compiling for the Raspberry Pi.  None of them worked as the compile targets/tools were wrong.  Here's what worked for me.  The target boxes in this case are running 64 bit versions of Ubuntu 22.04.

I'm doing all the building on Ubuntu 22.04 x86_64

===== Install the Rust Target =====
The target you are wanting to install is ''aarch64-unknown-linux-gnu''.
<code rust>
rustup target add aarch64-unknown-linux-gnu
</code>

===== Install the Necessary Build Tools =====
You'll actually need to install the appropriate build tools, specifically for the linking portion of the build.

<code bash>
sudo apt install g++-12-aarch64-linux-gnu
</code>

===== Set the Linker in Your Cargo Project =====
In the root of your Rust project you want to build (where your ''Cargo.toml'' file is), do the following:

<code bash>
# You have to create a build config with the linker set appropriately
mkdir .cargo
cat <<"EOF" > .cargo/config.toml
[build]

[target.aarch64-unknown-linux-gnu]
linker = "aarch64-linux-gnu-g++-12"
EOF

# Now you can build!
cargo build --release --target aarch64-unknown-linux-gnu
</code>