regression: add test case 1039 for subkey

Adds test case 1039 for testing a TA signed with a hierarchy of subkeys.

Reviewed-by: Jerome Forissier <jerome.forissier@linaro.org>
Signed-off-by: Jens Wiklander <jens.wiklander@linaro.org>
diff --git a/host/xtest/Makefile b/host/xtest/Makefile
index af45f5e..36c7e3d 100644
--- a/host/xtest/Makefile
+++ b/host/xtest/Makefile
@@ -137,6 +137,8 @@
 CFLAGS += -I../../ta/large/include
 CFLAGS += -I../../ta/supp_plugin/include
 CFLAGS += -I../../ta/bti_test/include
+CFLAGS += -I../../ta/subkey1/include
+CFLAGS += -I../../ta/subkey2/include
 
 TA_DIR ?= /lib/optee_armtz
 CFLAGS += -DTA_DIR=\"$(TA_DIR)\"