title: Makefile cannot find include path
body: <p>A Makefile in the subdirectory of my project doesn't see the include path ONLY when it is used from the main Makefile of my project.  I don't have much experience with Makefiles and a lot of what I've been reading is pretty confusing.  Here is the layout of my directory (with what I have so far since I just started the project):</p>
  
  <pre><code>main/
      Inventory/
          Item.h
          Item.cpp
          Makefile
      tools/
          include/
              json/
                  json.h
          jsoncpp.cpp
          Makefile
      main.cpp
      Makefile
  </code></pre>
  
  <p>Here is the Makefile in the main directory:</p>
  
  <pre><code>INCLUDE = -IInventory/
  CC = g++
  DEP = tools/jsoncpp.o Inventory/Item.o
  
  Main: main.o $(DEP)
      cd tools/ &amp;&amp; make
      cd Inventory/ &amp;&amp; make
      $(CC) -o Main main.o $(DEP) $(INCLUDE)
  
  main.o main.cpp
      $(CC) -c main.cpp $(INCLUDE)
  </code></pre>
  
  <p>Here is the Makefile in the tools directory:</p>
  
  <pre><code>INCLUDE = -Iinclude/
  CC = g++
  
  jsoncpp.o: jsoncpp.cpp
      $(CC) -c jsoncpp.cpp $(INCLUDE)
  </code></pre>
  
  <p>When I call make from the tools/, it works just fine. But when I call make from the main directory I get this error:</p>
  
  <pre><code>g++    -c -o tools/jsoncpp.o tools/json.cpp
  tools/jsoncpp.cpp:76:23: fatal error: json/json.h: No such file or directory
  #include "json/json.h"
                        ^
  compilation terminated.
  </code></pre>
  
  <p>Now I partially believe that it can't find the include directory for whatever reason, but the first line in that error is fairly odd to me because of that weird gap between g++ and -c.  Since my project will soon get pretty big, how can I fix this?</p>