The first two lines of src_prepare() still prevent FDT support from being enabled, in spite of the use_enable fdt in src_configure(). Simple fix.
The problem remains in the recently committed qemu-kvm-0.12.2.
I can simply remove it since its not really something that will get much support anyway if you so desire.
Understandable, but I don't think it's entirely necessary - I just noticed that the USE flag had been turned back on but wasn't entirely enabled. FDT seems useful, if for development. All fixing this will take is removing the first two lines in src_prepare(). If it is broken, then I'd see that as more a problem for upstream.
fixed in 0.12.2-r2