sim: run: add --argv0 option to control argv[0]

We default argv[0] to the program we run which is a standard *NIX
convention, but sometimes we want to be able to control the argv[0]
setting independently (especially for programs that inspect argv[0]
to change their behavior or output).  Add an option to control it.

sim/common/sim-utils.c

@@ -98,6 +98,7 @@ sim_state_free (SIM_DESC sd)
 #endif
 
   free (STATE_PROG_FILE (sd));
+  free (STATE_PROG_ARGV0 (sd));
   free (sd);
 }