Fix incorrect info in README

Author: astapleton

README.md

@@ -73,9 +73,9 @@ a number of fantastic resources available to help.
 
 ## Running unit tests
 
-First, you'll need to install the `aarch64-unknown-linux-gnu` target to run unit tests.
+If you're on a linux host, you can simply run unit tests with:
 
-If you're on a linux host, you can to run unit tests with `cargo test`.
+    cargo test --target x86_64-unknown-linux-gnu --tests --features stm32h503
 
 If you're not, you'll need to install [`cross`](https://github.com/cross-rs/cross), which is a cross compilation tool. See the `cross` instructions for details of installation and use. Once that is installed, using `cross test` will run the unit tests within a docker image.