Preserve inline `ghc-options` formatting from existing `.cabal` file

[webdevred]

Problem:
hpack merges multiple ghc-options entries into a single line or changes indentation. Related: #617

Expected behavior:
Keep each ghc-options entry on its own line with the original indentation.

Example:

-- Before (Gild-formatted)

ghc-options:
  -Wall
  -Wcompat
  -Widentities

-- After (hpack)

ghc-options: -Wall -Wcompat -Widentities