32bit-ci: pin GHC to 9.6.7 (#597)

The i386 job installed ghcup's "recommended" GHC, which is unpinned. When
the recommended version moved to 9.10.3, its deb10 i386 bindist's
`make install` started failing on the i386/ubuntu:bionic container,
breaking CI on every PR (#596).

Pin to 9.6.7 (deb9 bindist), the last version known to install on this
container, so metadata bumps can't break CI unannounced.

Closes #596

Co-authored-by: Claude Opus 4.8 <noreply@anthropic.com>

Author: sjakobi

.github/workflows/32bit-ci.yml

@@ -22,7 +22,9 @@ jobs:
       run: |
         apt-get update -y
         apt-get install -y autoconf build-essential zlib1g-dev libgmp-dev curl libncurses5 libtinfo5 libncurses5-dev libtinfo-dev
-        curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | BOOTSTRAP_HASKELL_NONINTERACTIVE=1 BOOTSTRAP_HASKELL_INSTALL_NO_STACK=1 sh
+        # Pin the GHC version: the i386/ubuntu:bionic container can't run the
+        # deb10 i386 bindist that ghcup's "recommended" GHC moved to (see #596).
+        curl --proto '=https' --tlsv1.2 -sSf https://get-ghcup.haskell.org | BOOTSTRAP_HASKELL_NONINTERACTIVE=1 BOOTSTRAP_HASKELL_INSTALL_NO_STACK=1 BOOTSTRAP_HASKELL_GHC_VERSION=9.6.7 sh
     - uses: actions/checkout@v1 #This version must stay old enough to remain compatible with the container image
     - name: Test
       run: |