README: development nightly notes improved

README.md

@@ -101,14 +101,25 @@ nightly version, which was known to work:
 ```shell
 % rustup toolchain install nightly-2024-02-01
 % rustup target add wasm32-unknown-unknown --toolchain nightly-2024-02-01
-% sed -i Makefile -e "s|nightly|nightly-2024-02-01|g"
 ```
 
-When using cargo directly, you have to add the `+nightly-2024-02-01` flag,
-in order for it to use the older nightly version.
+Now we can use that toolchain in `make` directly:
+
+```shell
+% make CARGO="cargo +nightly-2024-02-01" {target}
+```
+
+Or, if we are lazy, we can modify the `Makefile` to always use that:
+
+```shell
+% sed -i Makefile -e "s|nightly|nightly-2024-02-01|g"
+```
 
 Under no circumstances commit or push the Makefile change.
 
+When using `cargo` directly, you have to add the `+nightly-2024-02-01` flag,
+in order for it to use the older nightly version.
+
 ## Install
 
 This will install the binaries on your system (`/usr/local` by