if map_library has allocated a buffer for phdrs, free it on success too

this fixes an oversight in the previous commit.

src/ldso/dynlink.c

@@ -421,6 +421,7 @@ static void *map_library(int fd, struct dso *dso)
 	dso->base = base;
 	dso->dynv = (void *)(base+dyn);
 	if (dso->tls_size) dso->tls_image = (void *)(base+tls_image);
+	free(allocated_buf);
 	return map;
 noexec:
 	errno = ENOEXEC;