[Haskell-cafe] How to set ghc options while building Setup.hs in cabal package?

[Magicloud Magiclouds]

Hi,

I have some code in Setup.hs in a cabalized project. I'd like them to
be warning-free. But I could not find a way to set -Wall.

I tried ghc-options in ~/.cabal/config. But seems like it did not kick in.

```
/bin/ghc --make -fbuilding-cabal-package -odir
/home/shida/src/Personal/cairo-core/dist-newstyle/build/x86_64-linux/ghc-8.6.3/cairo-core-1.16.0/setup
-hidir /home/shida/src/Personal/cairo-core/dist-newstyle/build/x86_64-linux/ghc-8.6.3/cairo-core-1.16.0/setup
-i -i/home/shida/src/Personal/cairo-core/. -optP-include
-optP/home/shida/src/Personal/cairo-core/dist-newstyle/build/x86_64-linux/ghc-8.6.3/cairo-core-1.16.0/setup/setup_macros.h
-hide-all-packages -no-user-package-db -package-db
/home/shida/.cabal/store/ghc-8.6.3/package.db -package-db
/home/shida/src/Personal/cairo-core/dist-newstyle/packagedb/ghc-8.6.3
-package-id Cabal-2.4.0.1 -package-id base-4.12.0.0 -package-id
directory-1.3.3.0 -package-id filepath-1.4.2.1 -package-id
haskell-src-exts-1.21.0-f3e84a9ee8883b0dcaaaaba712d74996854b441aa843a4dedc055c685debcfdb
/home/shida/src/Personal/cairo-core/dist-newstyle/build/x86_64-linux/ghc-8.6.3/cairo-core-1.16.0/setup/setup.hs
-o /home/shida/src/Personal/cairo-core/dist-newstyle/build/x86_64-linux/ghc-8.6.3/cairo-core-1.16.0/setup/setup
-threaded
```
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