btf_encoder: Discard CUs after BTF encoding

When doing BTF encoding/deduping, DWARF CUs are never used after BTF encoding
is done, so there is no point in wasting memory and keeping them in memory. So
discard them immediately.

Committer testing:

  $ pahole -J vmlinux
  $ ./btfdiff vmlinux
  $

Signed-off-by: Andrii Nakryiko <[email protected]>
Tested-by: Arnaldo Carvalho de Melo <[email protected]>
Cc: Alexei Starovoitov <[email protected]>
Cc: Andrii Nakryiko <[email protected]>
Cc: [email protected]
Cc: [email protected]
Cc: [email protected]
Signed-off-by: Arnaldo Carvalho de Melo <[email protected]>

Author: anakryiko

pahole.c

@@ -2384,7 +2384,7 @@ static enum load_steal_kind pahole_stealer(struct cu *cu,
 			fprintf(stderr, "Encountered error while encoding BTF.\n");
 			exit(1);
 		}
-		return LSK__KEEPIT;
+		return LSK__DELETE;
 	}
 
 	if (ctf_encode) {