xfree86: Fix meson overwriting suid wrapper with the wrapped executable

Meson gets confused when there are two targets of the same name within
the same directory, so we use a different intermediate name.

This is a problem with the Xorg SUID wrapper which has the same filename
as the real Xorg executable and is configured in the same meson.build
file. This commit works around this by using a different filename in
build stage and renaming only when installing.

Signed-off-by: Povilas Kanapickas <povilas@radix.lt>
4 jobs for meson-suid-wrapper-overwrite-fix in 4 minutes and 36 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Docker Image
passed #8325727
debian-buster

00:00:08

 
  Build And Test
passed #8325728
autotools

00:04:27

passed #8325729
meson

00:01:42

passed #8325730
meson-noglamor

00:01:29