Problems in using make – usb.h not found

I am trying to use make to build a binary from a source code for a program I need.

Link to source: https://github.com/pali/0xFFFF

It requires usb.h, which seems to be part of usblib-compat. I installed the latter by brew install usblib-compat. But still usb.h can't be seen, although I know where it is (under /usr/local/Cellar/usblib-compat/version/include).

I read a lot over the Internet and tried to set many environment variables, but no success. Any idea?

UPDATE

After many trials, I have progressed somehow. Namely, the file config.mk is clearly read during the make'ing process, although I have to admit that it is not clear to me how this is done; anyway, I noticed two lines commented:

CPPFLAGS += -I/usr/local/include
LDFLAGS += -L/usr/local/lib -Wl,-R/usr/local/lib

I uncommented them and now something happens: the usb.h is found. I think the first of these variable definitions tells the compiler where to look tor header files, and the second tells the linker where to look for libraries – but again it is not completely clear to me.

In any case, I have still problems. Namely, the make'ing process outputs two warnings and an error, and then stops:

usb-device.c:90:57: warning: unused parameter 'udev' [-Wunused-parameter]
static void usb_reattach_kernel_driver(usb_dev_handle * udev, int interface) {
                                                        ^
usb-device.c:90:67: warning: unused parameter 'interface' [-Wunused-parameter]
static void usb_reattach_kernel_driver(usb_dev_handle * udev, int interface) {

usb-device.c:324:13: error: use of undeclared identifier 'RTLD_DEFAULT' if ( dlsym(RTLD_DEFAULT, "libusb_init") )

Seems this program is difficult to port from Linux to Mac, although I think it should be portable. If anyone has any idea about what to do (apart from running a Linux distribution…), it would be much appreciated.