kbuild: descend into scripts/gcc-plugins/ via scripts/Makefile

Now that 'archprepare' depends on 'scripts', Kbuild can descend into
scripts/gcc-plugins in a more standard way.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Reviewed-by: Kees Cook <keescook@chromium.org>

Makefile

@@ -1110,7 +1110,7 @@ prepare1: prepare2 $(version_h) $(autoksyms_h) include/generated/utsrelease.h
 
 macroprepare: prepare1 archmacros
 
-archprepare: archheaders archscripts macroprepare scripts gcc-plugins
+archprepare: archheaders archscripts macroprepare scripts
 
 prepare0: archprepare
 	$(Q)$(MAKE) $(build)=scripts/mod

scripts/Makefile

@@ -36,9 +36,10 @@ PHONY += build_unifdef
 build_unifdef: $(obj)/unifdef
 	@:
 
+subdir-$(CONFIG_GCC_PLUGINS) += gcc-plugins
 subdir-$(CONFIG_MODVERSIONS) += genksyms
 subdir-$(CONFIG_SECURITY_SELINUX) += selinux
 subdir-$(CONFIG_GDB_SCRIPTS) += gdb
 
 # Let clean descend into subdirs
-subdir-	+= basic dtc kconfig mod package gcc-plugins
+subdir-	+= basic dtc kconfig mod package

scripts/Makefile.gcc-plugins

@@ -49,11 +49,3 @@ KBUILD_CFLAGS += $(GCC_PLUGINS_CFLAGS)
 # All enabled GCC plugins are collected here for building below.
 GCC_PLUGIN := $(gcc-plugin-y)
 export GCC_PLUGIN
-
-# Actually do the build, if requested.
-PHONY += gcc-plugins
-gcc-plugins: scripts_basic
-ifdef CONFIG_GCC_PLUGINS
-	$(Q)$(MAKE) $(build)=scripts/gcc-plugins
-endif
-	@: