lirc-tools: add patch to fix parallel build issue

The lirc-tools package fails to build once in a while in the
autobuilders. Some quick analysis of the problematic Makefile.am has
revealed one issue. However, since the issue is difficult to
reproduce, we could only check that the new solution continue to work,
and we're not 100% sure it fixes the entire problem: only the
autobuilders can say, over time.

Supposedly fixes:

  http://autobuild.buildroot.org/results/eb47d57de8182d25b1dacbf0ac3726ed20063d04/



Signed-off-by: Thomas Petazzoni <thomas.petazzoni@free-electrons.com>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>