Add DUB install to VM initialization. (#8992)

Author: LightBender

.github/workflows/main.yml

@@ -51,6 +51,10 @@ jobs:
       - uses: actions/checkout@v4
         with:
           fetch-depth: 50
+
+      - name: Install Host D compiler
+        uses: dlang-community/setup-dlang@v1
+
       - name: Clone DMD
         run: |
           set -uexo pipefail
@@ -131,6 +135,10 @@ jobs:
       - uses: actions/checkout@v4
         with:
           fetch-depth: 50
+
+      - name: Install Host D compiler
+        uses: dlang-community/setup-dlang@v1
+
       - name: Run in VM
         uses: cross-platform-actions/action@v0.23.0
         with: