message: build: check for existence of 0 instead of string comparisons
diff: @@ -55,7 +55,9 @@ export EXAMPLES_DIR
  CPU_CORES=$(nproc --all)
  # Build debug binary
  -if [ -n "$RUSTUP" ] && [ "$RUSTUP" -eq 1 ]; then
  +# Check if the variabl $RUSTUP is set. If yes the $TOOLCHAIN can be choosen via cargo, otherwise cargo might not now
  +# about that feature.
  +if [ -v RUSTUP ]; then
  cargo +$TOOLCHAIN build
  else
  cargo build
  