Now that we include the Kerberos tests, we need to include
AM_CPPFLAGS in the CPPFLAGS for libtap.
check_LIBRARIES = tests/tap/libtap.a
tests_runtests_CPPFLAGS = -DSOURCE='"$(abs_top_srcdir)/tests"' \
-DBUILD='"$(abs_top_builddir)/tests"'
-tests_tap_libtap_a_CPPFLAGS = -I$(abs_top_srcdir)/tests
+tests_tap_libtap_a_CPPFLAGS = -I$(abs_top_srcdir)/tests $(AM_CPPFLAGS)
tests_tap_libtap_a_SOURCES = tests/tap/basic.c tests/tap/basic.h \
tests/tap/kerberos.c tests/tap/kerberos.h tests/tap/macros.h \
tests/tap/messages.c tests/tap/messages.h tests/tap/process.c \