build: make coverage recipe use rustup stable

Signed-off-by: Luca Muscariello <muscariello@ieee.org>

Author: muscariello

justfile

@@ -37,7 +37,8 @@ check: fmt-check lint test
 
 # Generate code coverage report (requires cargo-llvm-cov)
 coverage:
-    cargo llvm-cov --workspace --html --ignore-filename-regex 'gen/'
+    rustup component add llvm-tools-preview --toolchain stable
+    rustup run stable cargo llvm-cov --workspace --html --ignore-filename-regex 'gen/'
     @echo "Coverage report: target/llvm-cov/html/index.html"
 
 # Run the helloworld example