revert util/time_limit.h OR_DLL remove

ortools/util/time_limit.h

@@ -38,7 +38,7 @@
  * Enables changing the behavior of the TimeLimit class to use -b usertime
  * instead of \b walltime. This is mainly useful for benchmarks.
  */
-ABSL_DECLARE_FLAG(bool, time_limit_use_usertime);
+OR_DLL ABSL_DECLARE_FLAG(bool, time_limit_use_usertime);
 
 namespace operations_research {
 
@@ -91,7 +91,7 @@ namespace operations_research {
  */
 // TODO(user): The expression "deterministic time" should be replaced with
 //                 "number of operations" to avoid confusion with "real" time.
-class TimeLimit {
+class OR_DLL TimeLimit {
  public:
   static const double kSafetyBufferSeconds;  // See the .cc for the value.
   static const int kHistorySize;