Log Message:
sysutils/flashrom: Declare dependency on libusb1.

And pass in the necessary -I flag.

Resolves:

Checking for libusb-1.0 headers... not found.

The following features require libusb-1.0: CONFIG_PICKIT2_SPI \ 
CONFIG_STLINKV3_SPI CONFIG_DEDIPROG CONFIG_DEVELOPERBOX_SPI CONFIG_CH341A_SPI \ 
CONFIG_DIGILENT_SPI.
Please install libusb-1.0 headers or disable all features
mentioned above by specifying make CONFIG_ENABLE_LIBUSB1_PROGRAMMERS=no
See README for more information.