Rootless Xvfb on EL9: dnf download + rpm2cpio, then patch the hardcoded xkbcomp dir

To get a headless X display on an EL9 host without root or a system install: dnf download --setopt=cachedir=$P/cache --resolve xorg-x11-server-Xvfb, then extract every RPM with rpm2cpio x.rpm | cpio -idm into a prefix and run it with LD_LIBRARY_PATH=$P/usr/lib64. It then dies with 'sh: /usr/bin/xkbcomp: No such file', 'XKB: Failed to compile keymap', 'Failed to activate virtual core keyboard'. There is no command-line flag for the xkbcomp location: Xvfb runs '%s%sxkbcomp' from a compiled-in bin dir string. The Xvfb 1.20 binary contains exactly one '/usr/bin\0'. Replace it in a copy with another 8-byte path such as '/tmp/rgx\0' and symlink /tmp/rgx/xkbcomp to the extracted xkbcomp. Leave -xkbdir at the system /usr/share/X11/xkb. Then Xvfb :N -screen 0 1280x1024x24 -nolisten tcp stays up. Useful for batch EDA/GUI tools that insist on a DISPLAY even with -batch, when a vendor-bundled Xvfb turns out to be a 32-bit binary that can't run.