kbuild: hide tools/ build targets from external module builds

The tools/ directory only exists in the kernel source tree, not in
external modules.

Do not expose the meaningless targets to external modules.
Signed-off-by: Masahiro Yamada <masahiroy@kernel.org>

Makefile

@@ -1351,6 +1351,22 @@ PHONY += scripts_unifdef
 scripts_unifdef: scripts_basic
 	$(Q)$(MAKE) $(build)=scripts scripts/unifdef
 
+# ---------------------------------------------------------------------------
+# Tools
+
+# Clear a bunch of variables before executing the submake
+ifeq ($(quiet),silent_)
+tools_silent=s
+endif
+
+tools/: FORCE
+	$(Q)mkdir -p $(objtree)/tools
+	$(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/
+
+tools/%: FORCE
+	$(Q)mkdir -p $(objtree)/tools
+	$(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/ $*
+
 # ---------------------------------------------------------------------------
 # Kernel selftest
 
@@ -1951,20 +1967,6 @@ kernelversion:
 image_name:
 	@echo $(KBUILD_IMAGE)
 
-# Clear a bunch of variables before executing the submake
-
-ifeq ($(quiet),silent_)
-tools_silent=s
-endif
-
-tools/: FORCE
-	$(Q)mkdir -p $(objtree)/tools
-	$(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/
-
-tools/%: FORCE
-	$(Q)mkdir -p $(objtree)/tools
-	$(Q)$(MAKE) LDFLAGS= MAKEFLAGS="$(tools_silent) $(filter --j% -j,$(MAKEFLAGS))" O=$(abspath $(objtree)) subdir=tools -C $(srctree)/tools/ $*
-
 quiet_cmd_rmfiles = $(if $(wildcard $(rm-files)),CLEAN   $(wildcard $(rm-files)))
       cmd_rmfiles = rm -rf $(rm-files)