backport from main:

* bump abseil to 20250814
* bump protobuf to v32.0
* cmake: add ccache auto support
* backport flatzinc, math_opt and sat update

ortools/sat/samples/OptionalIntervalSampleSat.java

@@ -11,6 +11,7 @@
 // See the License for the specific language governing permissions and
 // limitations under the License.
 
+// [START program]
 package com.google.ortools.sat.samples;
 
 import com.google.ortools.Loader;
@@ -45,3 +46,4 @@ public class OptionalIntervalSampleSat {
     System.out.println(fixedInterval);
   }
 }
+// [END program]