respect NDEBUG.

ko1 · ko1 · commit 63160a84b42c · 2019-07-19T12:04:32.000+09:00
ruby/ruby.h includes ruby/assert.h, and RUBY_NDEBUG is defined
by checking NDEBUG. In other words, NDEBUG is only seen just
after ruby/ruby.h. This patch also cheks NDEBUG just after
including ruby_assert.h.

Without this patch, assertions in array.c are always enabled.
diff --git a/ruby_assert.h b/ruby_assert.h
@@ -8,3 +8,8 @@
 #undef assert
 #define assert RUBY_ASSERT
 #endif
+
+#ifdef NDEBUG
+  #undef  RUBY_NDEBUG
+  #define RUBY_NDEBUG 1
+#endif
