1.6.10 won't compile my project, fails on normal #include

[i-make-robots]

https://github.com/MarginallyClever/Makelangelo-firmware/tree/master/firmware_ams/firmware_ams.ino
calls

#include "AFMotorDrawbot/AFMotorDrawbot.h"

which exists. Tests on windows 10 and linux systems both fail on this line.
someone in irc #arduino said that gcc was compiling with -E and that seemed wierd to them. IDK.

[matthijskooijman]

I believe this is a duplicate of #5186, which got introduced in 1.6.10 and will be fixed in 1.6.11 in the coming days. Testing the release candidate would be appreciated: #5208 (comment)