Minimal config fails on some hosts

This minimal build fails:

./waf clean && ./waf configure && ./waf build  

The error is:

[66/93] Compiling ntpfrob/main.c
../../ntpd/ntpd.c: In function 'ntpdmain':
../../ntpd/ntpd.c:833:39: error: 'debug' undeclared (first use in this function)
      fprintf(stdout, "#debug = %d\n", debug);

The problem is a missing #ifdef DEBUG around line 833