GHA: make macOS build step verbose with cmake [ci skip]

To match autotools, and to allow comparing command-lines.

.github/workflows/ci.yml

@@ -1102,7 +1102,7 @@ jobs:
       - name: 'build'
         run: |
           if [ "${MATRIX_BUILD}" = 'CM' ]; then
-            cmake --build bld
+            cmake --build bld --verbose
           else
             make -C bld -j4 V=1
           fi