Restore failure returns to unexaix.c, unexcoff.c, unexcw.c

src/unexaix.c

@@ -142,6 +142,7 @@ unexec (const char *new_name, const char *a_name)
       || unrelocate_symbols (new, a_out, a_name, new_name) < 0)
     {
       close (new);
+      return;
     }
 
   close (new);

src/unexcoff.c

@@ -545,6 +545,7 @@ unexec (const char *new_name, const char *a_name)
       )
     {
       close (new);
+      return;
     }
 
   close (new);

src/unexcw.c

@@ -263,6 +263,7 @@ unexec (const char *outfile, const char *infile)
     {
       /* can only dump once */
       printf ("You can only dump Emacs once on this platform.\n");
+      return;
     }
 
   report_sheap_usage (1);