add exit() to one() functions since compilers may not recognize that MPI_Abort() does not return.

src/error.cpp

@@ -107,6 +107,7 @@ void Error::universe_one(const std::string &file, int line, const std::string &s
   throw LAMMPSAbortException(mesg, universe->uworld);
 #else
   MPI_Abort(universe->uworld,1);
+  exit(1); // to trick "smart" compilers into believing this does not return
 #endif
 }
 
@@ -205,6 +206,7 @@ void Error::one(const std::string &file, int line, const std::string &str)
   if (screen) fflush(screen);
   if (logfile) fflush(logfile);
   MPI_Abort(world,1);
+  exit(1); // to trick "smart" compilers into believing this does not return
 #endif
 }