libctf, create: empty dicts are dirty to start with

Without this, an empty dict that is written out immediately never gets
any content at all: even the header is left empty.

libctf/
	* ctf-create.c (ctf_create): Mark dirty.

libctf/ctf-create.c

@@ -126,6 +126,7 @@ ctf_create (int *errp)
   fp->ctf_dtoldid = 0;
   fp->ctf_snapshots = 1;
   fp->ctf_snapshot_lu = 0;
+  fp->ctf_flags |= LCTF_DIRTY;
 
   ctf_set_ctl_hashes (fp);
   ctf_setmodel (fp, CTF_MODEL_NATIVE);