File vbox-buildfix of Package virtualbox-ose

--- VirtualBox-2.0.4/Config.kmk
+++ VirtualBox-2.0.4/Config.kmk
@@ -1798,7 +1798,8 @@
     kernelpath := $(realpath $(VBOX_LINUX_SRC)/$(kernelsrc))
    else
     # Linux >= 2.6.25
-    kernelpath := $(shell $(SED_EXT) -ne 's+^MAKEARGS *:= *-C *\(.*\)+\1+p' $(VBOX_LINUX_SRC)/Makefile)
+    kernelsrc := $(shell $(SED_EXT) -ne 's+^MAKEARGS *:= *-C *\(.*\)+\1+p' $(VBOX_LINUX_SRC)/Makefile)
+    kernelpath := $(realpath $(VBOX_LINUX_SRC)/$(kernelsrc))
    endif
    ifneq ($(kernelpath),)
     VBOX_LINUX_INCS                 += $(VBOX_LINUX_SRC)/include2 $(kernelpath)/include