Description: Pass 'mathjax' to Haddock
 Hadrian currently doesn't allow us to modify Haddock options, so
 patch Hadrian to manually pass the 'mathjax' option.
Author: Ilias Tsitsimpis <iliastsi@debian.org>
Bug: https://gitlab.haskell.org/ghc/ghc/-/issues/23625

--- a/hadrian/src/Settings/Builders/Haddock.hs
+++ b/hadrian/src/Settings/Builders/Haddock.hs
@@ -30,6 +30,7 @@
             , arg "-o", arg $ takeDirectory output
             , arg "-t", arg "Haskell Hierarchical Libraries"
             , arg "-p", arg "libraries/prologue.txt"
+            , arg "--mathjax=file:///usr/share/javascript/mathjax/MathJax.js"
             , pure [ "--read-interface="
                      ++ (takeFileName . takeDirectory) haddock
                      ++ "," ++ haddock | haddock <- inputs ] ]
--- a/hadrian/src/Settings/Default.hs
+++ b/hadrian/src/Settings/Default.hs
@@ -237,8 +237,8 @@
 
 defaultHaddockExtraArgs :: Args
 defaultHaddockExtraArgs = builder (Haddock BuildPackage) ?
-  mconcat [ arg "--hyperlinked-source", arg "--hoogle", arg "--quickjump" ]
-
+  mconcat [ arg "--hyperlinked-source", arg "--hoogle", arg "--quickjump"
+          , arg "--mathjax=file:///usr/share/javascript/mathjax/MathJax.js" ]
 
 -- | Default source arguments, e.g. optimisation settings.
 defaultSourceArgs :: SourceArgs
