Check arguments when building manual tests

Manual tests require setting USE_NVM=1 and NEW_TEST_SESSION=0
otherwise they will not function properly (as test results will
not be preserved across reboots). We should check that these
variables have the required values during the build.

Change-Id: I72fc8a4badf107fe2ebd6bfb88631828e14a77b3
Signed-off-by: Paul Beesley <paul.beesley@arm.com>
diff --git a/tftf/tests/tests-manual.mk b/tftf/tests/tests-manual.mk
index fea81a1..bd8132b 100644
--- a/tftf/tests/tests-manual.mk
+++ b/tftf/tests/tests-manual.mk
@@ -11,3 +11,11 @@
 		reset2/reset2.c 					\
 		system_off/test_system_off.c 				\
 	)
+
+ifeq (${USE_NVM},0)
+$(error Manual tests require USE_NVM=1 to persist test results across reboots)
+endif
+
+ifeq (${NEW_TEST_SESSION},1)
+$(error Manual tests require NEW_TEST_SESSION=0 to persist test results across reboots)
+endif
\ No newline at end of file