ci: implement a (temporary) workaround to help switching to asciidoctor

We want to switch from using `asciidoctor-extensions` to using regular
`asciidoctor` instead (the custom macros are no longer needed).

To that end, we want to install `mingw-w64-asciidoctor`, but that would fail due
to a conflict with the `mingw-w64-asciidoctor-extensions` package:

  error: failed to commit transaction (conflicting files)
  mingw-w64-x86_64-asciidoctor: /mingw64/bin/asciidoctor exists in filesystem

Let's work around that by explicitly removing the latter package as
needed.

Signed-off-by: Johannes Schindelin <[email protected]>

Author: dscho

.github/workflows/main.yml

@@ -59,6 +59,13 @@ jobs:
           # reduce time required to install packages by disabling pacman's disk space checking
           sed -i 's/^CheckSpace/#CheckSpace/g' /etc/pacman.conf &&
 
+          # help git-sdk-arm64 switch from `asciidoc` to `asciidoctor`
+          {
+            test mingw-w64-git != '${{ matrix.directory }}' ||
+            test ! -d /var/lib/pacman/local/mingw-w64-*-asciidoctor-extensions-* ||
+            pacman -R --noconfirm mingw-w64-$MSYSTEM_CARCH-asciidoctor-extensions
+          } &&
+
           top_dir=$PWD &&
           cd "${{ matrix.directory }}" &&
           MAKEFLAGS=-j8 makepkg-mingw -s --noconfirm &&