Clone the void-packages-xanmod git repository and install the bootstrap packages:
$ git clone https://github.com/ivmask/void-packages-xanmod.git
$ cd void-packages-xanmod
$ ./xbps-src binary-bootstrap
Modify etc/conf to build packages marked as 'restricted'
$ echo XBPS_ALLOW_RESTRICTED=yes >> etc/conf
Build the desired kernel package by using:
$ ./xbps-src -f -jX linuxX.X-xanmod linuxX.X-xanmod-headers
Compiling time will depend on how much CPU threads are being used, and obviously, CPU specs. You can modify the number of used threads by changing the -jX flag, replacing 'X' with the desired number.
Once built, the package will be available in hostdir/binpkgs. To install it:
# sudo xbps-install --repository hostdir/binpkgs linuxX.X-xanmod linuxX.X-xanmod-headers
To finish the installation and make sure grub boot entries are added, use the xbps-reconfigure command.
$ sudo xbps-reconfigure -f linuxX.X-xanmod