feat(Makefile): enhance installation and cleanup process

Improves the installation process by ensuring the target directory
exists and adds a cleanup step to maintain a clean build environment.

- Add directory creation step in the install target to ensure
  $(PREFIX)/bin exists before installation.
- Introduce a clean target to remove the code-preloader binary,
  preventing stale binaries from affecting future builds.
  </message-format>

Signed-off-by: Glenn <glenux@glenux.net>

Makefile

@@ -14,9 +14,13 @@ test:
 	crystal spec --error-trace
 
 install:
+	mkdir -p $(PREFIX)/bin
 	install \
 		-m 755 \
 		bin/code-preloader \
 		$(PREFIX)/bin
 
+clean:
+	rm -f bin/code-preloader
+
 .PHONY: spec test build all prepare install