simplify by using utils::strdup()

src/compute_inertia_chunk.cpp

@@ -41,9 +41,7 @@ ComputeInertiaChunk::ComputeInertiaChunk(LAMMPS *lmp, int narg, char **arg) :
 
   // ID of compute chunk/atom
 
-  int n = strlen(arg[3]) + 1;
-  idchunk = new char[n];
-  strcpy(idchunk,arg[3]);
+  idchunk = utils::strdup(arg[3]);
 
   init();