doc: Show example of `configureFlags'.

Dependencies

• [2] 2LTNY56W doc: Add preliminary section about `release.nix'.
• [*] PKE6I67S doc: Import the "Creating Projects" chapter by Visser & Dolstra.

Change contents

• edit in doc/manual/projects.xml at line 212
  [2.2358]

  [2.2358]
  + configureFlags = [ "--disable-silent-rules" ];