[master] make sure generated resolverdef.h header is also found

This was noticed on the distcheck build.

src/bin/resolver/tests/Makefile.am

@@ -1,6 +1,7 @@
 AM_CPPFLAGS = -I$(top_srcdir)/src/lib -I$(top_builddir)/src/lib
 AM_CPPFLAGS += -I$(top_builddir)/src/lib/dns -I$(top_srcdir)/src/bin
 AM_CPPFLAGS += -I$(top_builddir)/src/lib/cc
+AM_CPPFLAGS += -I$(top_builddir)/src/bin/resolver
 AM_CPPFLAGS += -DTEST_DATA_DIR=\"$(top_srcdir)/src/lib/testutils/testdata\"
 AM_CPPFLAGS += -DTEST_DATA_BUILDDIR=\"$(abs_top_builddir)/src/lib/testutils/testdata\"
 AM_CPPFLAGS += $(BOOST_INCLUDES)