hpack currently only supports ghc-shared-options within a verbatim block.

ghc-shared-options: token list

Additional options for GHC when the package is built as shared library. The options specified via this field are combined with the ones specified via ghc-options, and are passed to GHC during both the compile and link phases.

https://cabal.readthedocs.io/en/latest/cabal-package.html#pkg-field-ghc-shared-options