title: waf does not correctly detect C++ #include dependencies
body: <p>I have C++ header file dependencies that I specify in my waf script with the  <code>includes=...</code> parameter to bld.program().</p>
  
  <p>I know the waf build configuration sees the includes because my program compiles correctly.</p>
  
  <p>However, when I change a header file, waf does not detect the change. That is, when I run <code>waf build</code> after changing the contents of an included header, nothing gets recompiled.</p>
  
  <p>Isn't waf supposed to determine #include "..." dependencies automatically?</p>
  
  <p>How can I troubleshoot this?</p>
  
  <p>I have looked in the build/c4che directory to see if I could make sense of the configuration files stored there. Mention of "include" in the waf generated .py files is suspiciously absent.</p>
  
  <p>I am using waf version 1.9.0.</p>
  
  <p>I have also tried this with waf 1.8.19 and got the same result.</p>
  
  <p>EDIT: I replaced my original complicated wscript with the much simpler one listed below, and I still get the same behavior.</p>
  
  <p>Here is my wscript:</p>
  
  <pre><code>top = '.'
  out = 'build'
  CXXFLAGS = ['-fopenmp', '-Wall', '-Werror', '-std=c++11', '-Wl,--no-as-needed']
  
  def options(ctx):
      ctx.load('compiler_cxx')
  
  def configure(ctx):
      ctx.load('compiler_cxx')
      ctx.env.CXXFLAGS = CXXFLAGS
  
  def build(ctx):
      ctx.program(source="test_config_parser.cpp", target="test_config_parser", includes=["../include"], lib=['pthread', 'gomp'])
  </code></pre>