Hello. A small issue (svn changeset 30537):
src\VBox\HostDrivers\Support\Makefile.kmk
line 158:
SUPR0IdcClient_SDKS.win = W2K3DDK WINPSDKINCS
It should be:
SUPR0IdcClient_SDKS.win = $(VBOX_WINDDK) WINPSDKINCS
Otherwise, the compilation process stops because of bad DDK path passed to cl.exe.