MinGW g++ doesn't find headers in its own include directory

Question

So I recently installed MinGW via the latest version of nuwen's MinGW distribution that includes the boost C++ libraries. Specifically, I was after the scoped_ptr that the boost library provides. However, when I try to include the scoped_ptr (#include <boost/scoped_ptr.hpp>) in my header, the compiler throws
error: boost/scoped_ptr.hpp: No such file or directory

Makefile:

compile:
    g++ -o gen/cavestory src/**.cc 
run:
    gen/cavestory

Also, I added a back version of SDL to MinGW's include directory under SDL/**. All of the header files are there, I've checked, and the compiler throws a similar error on my include SDL/SDL.h>.

Things I've tried:
Every variation of <> and "" in my include statements
Removing the .h and .hpp
Setting the compiler flags to specifically search the directories containing the headers with g++ -I

This code was compiling with an earlier version of MinGW, and the author of the MinGw distrobution specifically states that he changed the g++ compiler options to default to C++11, so I think it's very likely that it's something to do with that. My google-fu has not yeilded results, though.

Answer 1

Solution I came up with: based on Michael Burr's comment above I ran the compiler with the verbose flag. For some reason, the include directory that is searched is not located in the MinGw root directory, but buried in the lib directory. I expect that this was intended to be fixed with one of the installation scripts, but I either didn't run it correctly or it didn't work on my system. The directory where I needed to add the relevant files is, on my machine,

C:\MinGW\lib\gcc\x86_64-w64-mingw32\4.8.2\include

This is a quick-and-dirty fix. I'm sure that there's a better way, but this got me up and running the quickest.