community/xorg-server: allow rootless X server

This patch fixes the suid flag in /usr/libexec/Xorg.wrap (instead of /usr/libexec/Xorg) and installs the related wrapper script in /usr/bin/X, so rootless X server becomes possible without breaking systems that still needs root privileges to run X (e.g. GDM).

This is a follow up of !16022 (merged), which was reverted due to GDM issues requiring SUID bit on X (#12413 (closed)). This patch should work in this situation, as /usr/libexec/Xorg.wrap (called by /usr/bin/X) will check if X server can run without privileges, otherwise will start it as root. That's the same approach used by Debian, Void Linux and many other distros.