hmm, a couple of possible reasons:
i) did you change the firmware directory?
check its correct in preferences (i.e. pointing to where you have installed axoloti)
(you could also delete your axoloti.prefs file, to reset it, if your unsure)
ii) precompiled header
delete the build directory, and try again....
though it appears it was trying to build the precompiled header when it failed, so id guess (i)
(precompiled header is needed for even an empty patch, hence the failure)
bizarrely, I think your g++ line looks incorrect.. as its not got the firmware on the include path.
I say bizarrely, as others are using 1.0.12 on windows, so I cant see how it would be just you if there was an issue in the makefile, and the makefile is common to all platforms
edit2: actually the above probably confirms you have the firmware directory pointing to the wrong place, as the makefile lives in the firmware directory, and has been updated in 1.0.12