Fix Makefiles

[prezha]

Summary

• sole make should only call help
• fix command concatenation and remove unnecessary end-of-line in
  main Makefile
• add make clean to init-examples and aggregate it with main Makefile
• enable init-examples to be run from main Makefile and its own
  Makefile

Change Type

• Bug fix (resolves an issue without affecting existing features)
• Feature (adds new functionality without breaking changes)
• Breaking change (may impact existing functionalities or require documentation updates)
• Documentation (updates or additions to documentation)
• Refactoring or test improvements (no bug fixes or new functionality)

Review Checklist:

• Reviewed my own code for quality and clarity.
• Added comments to complex or tricky code sections.
• Updated any affected documentation.
• Included tests that validate the fix or feature.
• Checked that related changes are merged.

[prezha]

looks like only the TestCreateProfileStatusMultiRuleTransitions/0x90 test failed - probably not related to this change: could it be due to a race condition as these tests are run in parallel?

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edit: this could be related: #3299

[coveralls]

coverage: 51.964% (-0.02%) from 51.98%
when pulling b5647e3 on prezha:makefiles
into 586144c on stacklok:main.