Scons doesn't find boost header files
I'm trying to compile Ardour 2.0 from source but when I run Scons I get the following output:
scons: Reading SConscript files ...
Checking for usb_interrupt_write() in C library usb... no
Checking for FLAC__stream_decoder_new() in C++ library FLAC... no
Checking for C++ header file boost/shared_ptr.hpp... no
Boost header files do not appear to be installed.
I found a comment on the Ardour site saying that some distro's put the header files in a different location, but I checked and they are in /usr/include/boost, so that's good.
What could be wrong here?