tools build: Make fixdep parsing wait for last target

The fixdep tool, among other things, replaces the target of the object
in the gcc generated dependency output file.

The parsing code assumes there's only single target in the rule but this
is not always the case as described in here:

  https://gcc.gnu.org/ml/gcc-help/2016-11/msg00099.html



Make the fixdep code smart enough to skip all the possible targets.

Signed-off-by: Jiri Olsa <jolsa@kernel.org>
Tested-by: Arnaldo Carvalho de Melo <acme@redhat.com>
Acked-by: Peter Foley <pefoley2@pefoley.com>
Cc: Wang Nan <wangnan0@huawei.com>
Link: http://lkml.kernel.org/r/20161201130025.GA16430@krava


Signed-off-by: Arnaldo Carvalho de Melo <acme@redhat.com>