buildroot

qt: add patch to fix build on non-x86 platforms

This commit adds a patch to Qt that adjusts its build system to
properly support building on non-x86 platforms. The problem was due to
the PLATFORM and XPLATFORM variables having the same value when
building on a ppc64le system targetting an uncommon architecture
(Xtensa or ARC for example). We fix this problem by making sure
PLATFORM and XPLATFORM will always be different.

Fixes the following build failures occuring on gcc112 (a ppc64le
autobuilder machine):

  http://autobuild.buildroot.net/results/527747a2fbb31195bb6fdb37cfdaa624e69b7d68/
  (qt on xtensa)

  http://autobuild.buildroot.net/results/7db1265f6f34be3a498881564292517a8fc0e44e/
  (qt on ARC)

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