image-fit-sig: skip in tools build if key is missing

Skip signature verification in case no public key was given in order to
allow using fit_check_sign also to validate uImage.FIT images without
signatures. Guarded by USE_HOSTCC macro the behavior on target is
unchanged.

Signed-off-by: Daniel Golle <daniel@makrotopia.org>

boot/image-fit-sig.c

@@ -191,6 +191,11 @@ int fit_image_verify_required_sigs(const void *fit, int image_noffset,
 	int noffset;
 	int key_node;
 
+#ifdef USE_HOSTCC
+	if (!key_blob)
+		return 0;
+#endif
+
 	/* Work out what we need to verify */
 	*no_sigsp = 1;
 	key_node = fdt_subnode_offset(key_blob, 0, FIT_SIG_NODENAME);
@@ -477,6 +482,11 @@ static int fit_config_verify_required_keys(const void *fit, int conf_noffset,
 	bool reqd_policy_all = true;
 	const char *reqd_mode;
 
+#ifdef USE_HOSTCC
+	if (!key_blob)
+		return 0;
+#endif
+
 	/*
 	 * We don't support this since libfdt considers names with the
 	 * name root but different @ suffix to be equal