Add CI build for CP/M using z88dk

.github/workflows/ci.yml

@@ -199,3 +199,19 @@ jobs:
             sudo pkg update -f && sudo pkg install -y groff
             make linux LINUX_CC=cc
             make test
+
+  z88dk:
+    name: 'z88dk SDK'
+    runs-on: ubuntu-latest
+    container: 'z88dk/z88dk:latest'
+    steps:
+    - uses: actions/checkout@v4
+    - name: 'Show version'
+      run: zcc 2>&1 | head -1
+    - name: 'Compile with z88dk for CP/M'
+      # nroff is not available, so skip the man build
+      run: touch fvcbm.man && make cpm
+    - uses: actions/upload-artifact@v4
+      with:
+        name: 'fvcbm.com'
+        path: fvcbm