libtool: make sure autoheader run before automake

libtool: make sure autoheader run before automake

When use automake to generate Makefile.in from Makefile.am, there
comes below race:
 | configure.ac:45: error: required file 'config-h.in' not found

It is because the file config-h.in in updating process by autoheader,
so make automake run after autoheader to avoid the above race.

Signed-off-by: Mingli Yu <mingli.yu@windriver.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>