I edited my platformio.ini file in the master project:
[env:develop_mega]
framework = arduino
platform = atmelavr
board = megaatmega2560
build_flags = -DDEBUG -Ilib/NMEA_Parser/NMEA_Parser -Ilib/GPS_Driver/GPS_Driver
This compiles correctly on PlatformIO 2.8.6, actually.
None of my three projects are yet published to the PlatformIO registry, so I can’t use dependency tracking just yet. I will likely switch to that when or if I ever get to a publishable state.
The sub-libraries are intended to be completely public; I just have them parceled out for cleanliness.
I completely didn’t think of the -Ipath/to/libs option; mea culpa on that.
Thanks again for making this; I can’t imagine writing for Arduino in the native IDE anymore. I’ll try to give back after I graduate and can afford to be altruistic:p