Fix hakyll build: use proper src for subtasks.docs

I couldn't find out what was causing the website build to fail.

I looked back in the git history and since I remembered the code back in January
1st 2019 was working, I searched for the last commit from that period (before I
started working on it again recently).

This was the perfect use case for using git bisect.

After identifying a good commit back then (
55e947d7901c17dbb1365a5cfb9f40acd50e903b), I read the =git help bisect=
instructions, I only had to find the command to combine with =git bisect run= to
test each commit.

Initially I considered doing a simple or:
  nix-build -A subtasks.docs || nix-build -A build

This would work, but I later figured that the =publishScript= derivation existed
back then, and I could instead use it.

The final bisect commands were:
  git bisect start HEAD 55e947d7901c17dbb1365a5cfb9f40acd50e903b --
  git bisect run nix-build -A publishScript
  git bisect reset

After the second command and around 30 seconds and a lot of output, git said:
  error: build of '/nix/store/299c1mwcwxxl74cvzr13lzlfqfdqxdlc-publish.sh.drv' failed
  997bed0f60a8d09fa14544c0d4c489f771e2534c is the first bad commit
  commit 997bed0f60a8d09fa14544c0d4c489f771e2534c
  Author: EuAndreh <eu@euandre.org>
  Date:   Sun May 19 01:39:07 2019 -0300

      Split default.nix tasks

  :100644 100644 00572eb6a32da956d18b14e1c00323bba1b34a72 31feb5afc45ed2592b8f7a81b4ba7fe56fbe3fd1 M      default.nix
  bisect run success

After looking at how default.nix was before and after the bad commit, I realised
that the =src= attribute of the =subtasks.docs= derivation was adapted
incorrectly after being changed from the =build= derivation. After fixing it, it
worked :)

Great job git :)

1 files changed, 1 insertions, 0 deletions

diff --git a/default.nix b/default.nix
index fd02d59..8f66761 100644
--- a/default.nix
+++ b/default.nix
@@ -99,6 +99,7 @@ with pkgs.stdenv; rec {
     });
     docs = baseTask.overrideAttrs (baseAttrs: {
       name = "${baseAttrs.name}-docs";
+      src = ./site;
       buildInputs = [ websiteBuilder pandoc ];
       buildPhase = ''
         export LOCALE_ARCHIVE="${pkgs.glibcLocales}/lib/locale/locale-archive";