Pekka Paalanen authored Dec 07, 2016 and Adam Jackson committed Dec 07, 2016

Fix the following error on 'make distcheck':

make[6]: *** No rule to make target 'scripts/xvfb-piglit.sh', needed by 'scripts/xvfb-piglit.sh.log'.  Stop.
make[6]: Leaving directory '/home/pq/git/xserver/xorg-server-1.19.99.1/_build/sub/test'
Makefile:1367: recipe for target 'check-TESTS' failed

The setup to trigger this is:
  $ ./configure --prefix=/home/pq/local --disable-docs
  --disable-devel-docs --enable-xwayland --disable-xorg --disable-xvfb
  --disable-xnest --disable-xquartz --disable-xwin --enable-debug

SCRIPT_TESTS is populated conditionally, but we should distribute the
scripts in any case.

Reviewed-by: Adam Jackson <ajax@redhat.com>
Signed-off-by: Pekka Paalanen <pekka.paalanen@collabora.co.uk>