ct_test.c doesn't need to include from source top, only testutil.c does

The INCLUDE statement can handle setting extra include directories for
individual object files, let's use it.
Reviewed-by: NAndy Polyakov <appro@openssl.org>

test/build.info

@@ -204,9 +204,11 @@ INCLUDE[dtlsv1listentest]={- rel2abs(catdir($builddir,"../include")) -} .. ../in
 DEPEND[dtlsv1listentest]=../libssl
 
 SOURCE[ct_test]=ct_test.c testutil.c
-INCLUDE[ct_test]={- rel2abs(catdir($builddir,"../include")) -} ../crypto/include ../include ..
+INCLUDE[ct_test]={- rel2abs(catdir($builddir,"../include")) -} ../crypto/include ../include
 DEPEND[ct_test]=../libcrypto
 
 SOURCE[threadstest]=threadstest.c
 INCLUDE[threadstest]={- rel2abs(catdir($builddir,"../include")) -} .. ../include
 DEPEND[threadstest]=../libcrypto
+
+INCLUDE[testutil.o]=..