kbuild: drop superfluous GCC_PLUGINS_CFLAGS assignment

GCC_PLUGINS_CFLAGS is already in the environment, so it is superfluous
to add it in commandline of final build of init/.
Signed-off-by: NCao jin <caoj.fnst@cn.fujitsu.com>
Signed-off-by: NMasahiro Yamada <yamada.masahiro@socionext.com>

scripts/link-vmlinux.sh

@@ -246,7 +246,7 @@ else
 fi;
 
 # final build of init/
-${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init GCC_PLUGINS_CFLAGS="${GCC_PLUGINS_CFLAGS}"
+${MAKE} -f "${srctree}/scripts/Makefile.build" obj=init
 
 archive_builtin