sdistTarball requires all dependencies to be built, but this is not necessary

[ocharles]

Issue description

pkgs.haskell.lib.sdistTarball overrides a package's derivation to have a build phase that simply calls ./Setup sdist. However, all build inputs are retained, but these are not necessary. The current behavior means that sdistTarball cannot complete until all dependencies are built, but if you only need the tarball this delays the build.

I believe we can just add the following:

 configurePhase = ":";
 buildInputs = [];
 propagatedBuildInputs = [];

to sdistTarball.

[stale]

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[sternenseemann]

I would recommend using haskell.packages.*.cabalSdist added in #174176 for this purpose which avoids both building dependencies and even compiling Setup.hs.

(I'm not sure if emptying configurePhase would be okay, but avoiding deps compilation could still be possible in sdistTarball)

[ocharles]

I don't have any need for this anymore so I'm going to close this issue. It sounds like there is a good solution/workaround now, too!