GCC_PLUGIN_SUBDIR has never been used. If you really need this in
the future, please re-add it then.
For now, the code is unused. Remove.
'export HOSTLIBS' is not necessary either.
Signed-off-by: Masahiro Yamada <yamada.masahiro@socionext.com>
Signed-off-by: Kees Cook <keescook@chromium.org>