selftests: enforce local header dependency in lib.mk

Add local header dependency in lib.mk. This enforces the dependency
blindly even when a test doesn't include the file, with the benefit
of a simpler common logic without requiring individual tests to have
special rule for it.

Signed-off-by: Shuah Khan <[e-mail]>
Reviewed-by: Kees Cook <[e-mail]>
Signed-off-by: Shuah Khan <[e-mail]>

tools/testing/selftests/lib.mk

···
 # Selftest makefiles can override those targets by setting
 # OVERRIDE_TARGETS = 1.
 ifeq ($(OVERRIDE_TARGETS),)
-$(OUTPUT)/%:%.c
+LOCAL_HDRS := $(selfdir)/kselftest_harness.h $(selfdir)/kselftest.h
+$(OUTPUT)/%:%.c $(LOCAL_HDRS)
 	$(LINK.c) $^ $(LDLIBS) -o $@
 
 $(OUTPUT)/%.o:%.S