kbuild: fix make -rR breakage

make failed to supply the filename when using make -rR and using $(*F)
to get target filename without extension.
This bug was not reproduceable in small scale but using:
$(basename $(notdir $@)) fixes it with same functionality.

Signed-off-by: Sam Ravnborg <sam@ravnborg.org>
diff --git a/scripts/Makefile.host b/scripts/Makefile.host
index 2b066d1..18ecd4d 100644
--- a/scripts/Makefile.host
+++ b/scripts/Makefile.host
@@ -80,8 +80,10 @@
 #####
 # Handle options to gcc. Support building with separate output directory
 
-_hostc_flags   = $(HOSTCFLAGS)   $(HOST_EXTRACFLAGS)   $(HOSTCFLAGS_$(*F).o)
-_hostcxx_flags = $(HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) $(HOSTCXXFLAGS_$(*F).o)
+_hostc_flags   = $(HOSTCFLAGS)   $(HOST_EXTRACFLAGS)   \
+                 $(HOSTCFLAGS_$(basetarget).o)
+_hostcxx_flags = $(HOSTCXXFLAGS) $(HOST_EXTRACXXFLAGS) \
+                 $(HOSTCXXFLAGS_$(basetarget).o)
 
 ifeq ($(KBUILD_SRC),)
 __hostc_flags	= $(_hostc_flags)