hadrian: exclude cabal.project.symlink.broken from source archives

Cabal 3.14 introduced a broken symlink in its testsuite. Unfortunately,
this broke our source distribution as we use use `tar --dereference` to avoid
issues with symlink compatibility on windows, and `tar --dereference` chokes
when it encounters any broken symlinks.

We can't get rid of `--dereference` because symlinks are generally broken on
windows, so the only option is to exclude this file from source archives.

see also haskell/cabal#10442

hadrian/src/Rules/SourceDist.hs

@@ -55,8 +55,9 @@ archiveSourceTree prepare fname = do
  runBuilderWithCmdOptions
  [Cwd $ sourceDistRoot -/- dirName]
  (Tar Create)
- ["chJf", ".." -/- tarName, baseName]
- ["chJf", ".." -/- tarName] [baseName]
+ -- See https:/haskell/cabal/issues/10442 for why we exclude this file.
+ ["--exclude=cabal.project.symlink.broken","-chJf", ".." -/- tarName, baseName]
+ ["--exclude=cabal.project.symlink.broken","-chJf", ".." -/- tarName] [baseName]
 
 
 -- | This creates a symlink to the 'source' at 'target'