[Makefile.am] Minor

src/Makefile.am

diff --git a/src/Makefile.am b/src/Makefile.am
index 5ed6292..4a130e1 100644
--- a/src/Makefile.am
+++ b/src/Makefile.am
@@ -385,20 +385,22 @@
 dump_use_data_LDADD = libharfbuzz.la $(HBLIBS)
 
 COMPILED_TESTS = test-iter test-ot-tag test-unicode-ranges
+COMPILED_TESTS_CPPFLAGS = $(HBCFLAGS) -DMAIN -UNDEBUG
+COMPILED_TESTS_LDADD = libharfbuzz.la $(HBLIBS)
 check_PROGRAMS += $(COMPILED_TESTS)
 TESTS += $(COMPILED_TESTS)
 
 test_iter_SOURCES = test-iter.cc hb-static.cc
-test_iter_CPPFLAGS = $(HBCFLAGS) -DMAIN
-test_iter_LDADD = libharfbuzz.la $(HBLIBS)
+test_iter_CPPFLAGS = $(COMPILED_TESTS_CPPFLAGS)
+test_iter_LDADD = $(COMPILED_TESTS_LDADD)
 
 test_ot_tag_SOURCES = hb-ot-tag.cc
-test_ot_tag_CPPFLAGS = $(HBCFLAGS) -DMAIN
-test_ot_tag_LDADD = libharfbuzz.la $(HBLIBS)
+test_ot_tag_CPPFLAGS = $(COMPILED_TESTS_CPPFLAGS)
+test_ot_tag_LDADD = $(COMPILED_TESTS_LDADD)
 
 test_unicode_ranges_SOURCES = test-unicode-ranges.cc
-test_unicode_ranges_CPPFLAGS = $(HBCFLAGS) -DMAIN
-test_unicode_ranges_LDADD = libharfbuzz.la $(HBLIBS)
+test_unicode_ranges_CPPFLAGS = $(COMPILED_TESTS_CPPFLAGS)
+test_unicode_ranges_LDADD = $(COMPILED_TESTS_LDADD)
 
 TESTS_ENVIRONMENT = \
 	srcdir="$(srcdir)" \