[PATCH] build: Update configure.ac to support the latest automake.

[Chris Johns]

On 1/4/18 2:02 pm, Chris Johns wrote:
> On 1/4/18 1:58 pm, Joel Sherrill wrote:
>> Great job! 
> 
> Thanks. Simpler than I expected.
> 

Testing shows this change is not enough, more is needed to make this stuff work.

The error is:

config.status: error: in
`/opt/work/chris/rtems/kernel/bsps/xilinx_zynq_zedboard/arm-rtems5/c/xilinx_zynq_zedboard/testsuites/samples':
config.status: error: Something went wrong bootstrapping makefile fragments
    for automatic dependency tracking.  Try re-running configure with the
    '--disable-dependency-tracking' option to at least be able to build
    the package (albeit without support for automatic dependency tracking).
See `config.log' for more details

I cannot find too much about this and what is happening. I can see the
`leaf.cfg` link is not being made and so I can only guess something related to
`RTEMS_BSP_CONFIG_SUBDIR()` and `AC_CONFIG_SUBDIRS()` has changed which means
the `leaf.cfg` is not being made before samples is being configured.

Chris