Try a fix for a vbox issue

Author: jwodder

.github/workflows/build-macos.yaml

@@ -385,6 +385,13 @@ jobs:
         run: |
           # coreutils provides a readlink that supports `-f`
           brew install coreutils docker docker-machine
+
+          # <https://github.com/actions/virtual-environments/issues/4431>
+          brew uninstall virtualbox
+          cd "$(brew --repo homebrew/cask)"
+          git checkout 8670a72380c57c606d6582b645421e31dad2eee2
+          brew install --cask virtualbox
+
           mkdir -p ~/.docker/machine/cache
           wget -O ~/.docker/machine/cache/boot2docker.iso https://github.com/boot2docker/boot2docker/releases/download/v19.03.12/boot2docker.iso
           docker-machine --native-ssh create --driver virtualbox default

.github/workflows/build-ubuntu.yaml

@@ -53,7 +53,6 @@ jobs:
           sudo apt-get update -qq
           sudo apt-get install eatmydata
           sudo eatmydata apt-get install singularity-container gnupg moreutils strace
-          echo "just a touch to trigger workflow"
 
       - name: Determine git-annex ref to build
         run: |

.github/workflows/template/build-{{ostype}}.yaml.j2

@@ -605,6 +605,13 @@ jobs:
           {% if ostype == "macos" %}
           # coreutils provides a readlink that supports `-f`
           brew install coreutils docker docker-machine
+
+          # <https://github.com/actions/virtual-environments/issues/4431>
+          brew uninstall virtualbox
+          cd "$(brew --repo homebrew/cask)"
+          git checkout 8670a72380c57c606d6582b645421e31dad2eee2
+          brew install --cask virtualbox
+
           mkdir -p ~/.docker/machine/cache
           wget -O ~/.docker/machine/cache/boot2docker.iso https://github.com/boot2docker/boot2docker/releases/download/v19.03.12/boot2docker.iso
           docker-machine --native-ssh create --driver virtualbox default