[meson] keep asserts in test programs
diff --git a/src/meson.build b/src/meson.build
index d6c353e..5401e5d 100644
--- a/src/meson.build
+++ b/src/meson.build
@@ -712,7 +712,7 @@
     foreach name, source : noinst_programs
       executable(name, source,
         include_directories: incconfig,
-        cpp_args: cpp_args,
+        cpp_args: cpp_args + ['-UNDEBUG'],
         dependencies: libharfbuzz_dep,
         install: false,
       )