kbuild: add intermediate targets for Flex/Bison in scripts/Makefile.host

Flex and Bison are used only for host programs. Move their intermediate
target processing from scripts/Makefile.build to scripts/Makefile.host.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

scripts/Makefile.build

@@ -41,20 +41,6 @@ include $(srctree)/scripts/Makefile.compiler
 include $(kbuild-file)
 include $(srctree)/scripts/Makefile.lib
 
-# Do not include hostprogs rules unless needed.
-# $(sort ...) is used here to remove duplicated words and excessive spaces.
-hostprogs := $(sort $(hostprogs))
-ifneq ($(hostprogs),)
-include $(srctree)/scripts/Makefile.host
-endif
-
-# Do not include userprogs rules unless needed.
-# $(sort ...) is used here to remove duplicated words and excessive spaces.
-userprogs := $(sort $(userprogs))
-ifneq ($(userprogs),)
-include $(srctree)/scripts/Makefile.userprogs
-endif
-
 ifndef obj
 $(warning kbuild: Makefile.build is included improperly)
 endif
@@ -452,13 +438,24 @@ intermediate_targets = $(foreach sfx, $(2), \
 # %.asn1.o <- %.asn1.[ch] <- %.asn1
 # %.dtb.o <- %.dtb.S <- %.dtb <- %.dts
 # %.dtbo.o <- %.dtbo.S <- %.dtbo <- %.dtso
-# %.lex.o <- %.lex.c <- %.l
-# %.tab.o <- %.tab.[ch] <- %.y
 targets += $(call intermediate_targets, .asn1.o, .asn1.c .asn1.h) \
 	   $(call intermediate_targets, .dtb.o, .dtb.S .dtb) \
-	   $(call intermediate_targets, .dtbo.o, .dtbo.S .dtbo) \
-	   $(call intermediate_targets, .lex.o, .lex.c) \
-	   $(call intermediate_targets, .tab.o, .tab.c .tab.h)
+	   $(call intermediate_targets, .dtbo.o, .dtbo.S .dtbo)
+
+# Include additional build rules when necessary
+# ---------------------------------------------------------------------------
+
+# $(sort ...) is used here to remove duplicated words and excessive spaces.
+hostprogs := $(sort $(hostprogs))
+ifneq ($(hostprogs),)
+include $(srctree)/scripts/Makefile.host
+endif
+
+# $(sort ...) is used here to remove duplicated words and excessive spaces.
+userprogs := $(sort $(userprogs))
+ifneq ($(userprogs),)
+include $(srctree)/scripts/Makefile.userprogs
+endif
 
 # Build
 # ---------------------------------------------------------------------------

scripts/Makefile.host

@@ -160,3 +160,8 @@ $(host-rust): $(obj)/%: $(src)/%.rs FORCE
 
 targets += $(host-csingle) $(host-cmulti) $(host-cobjs) \
 	   $(host-cxxmulti) $(host-cxxobjs) $(host-rust)
+
+# %.lex.o <- %.lex.c <- %.l
+# %.tab.o <- %.tab.[ch] <- %.y
+targets += $(call intermediate_targets, .lex.o, .lex.c) \
+           $(call intermediate_targets, .tab.o, .tab.c .tab.h)