make: fix CAs copy issue

Acked-by: Jerome Forissier <jerome.forissier@linaro.org>
Signed-off-by: Igor Opaniuk <igor.opaniuk@linaro.org>
diff --git a/Makefile b/Makefile
index 8b0adc0..4d29a41 100644
--- a/Makefile
+++ b/Makefile
@@ -25,7 +25,7 @@
 	@mkdir -p $(OUTPUT_DIR)/ta
 	@mkdir -p $(OUTPUT_DIR)/ca
 	@for example in $(EXAMPLE_LIST); do \
-		if [ -e $$example/host/$$example ]; then \
+		if [ -e $$example/host/optee_$$example ]; then \
 			cp -p $$example/host/optee_$$example $(OUTPUT_DIR)/ca/; \
 		fi; \
 		cp -pr $$example/ta/*.ta $(OUTPUT_DIR)/ta/; \