no fallar si no existe /proc/sys/kernel/unprivileged_userns_clone

en fedora no existe ese archivo

$ make webpack-dev-server
make yarn
make[1]: se entra en el directorio '/home/librenauta/0xacab/sutty/behind-the-mask-jekyll-theme'
make hain args="yarn "
make[2]: se entra en el directorio '/home/librenauta/0xacab/sutty/behind-the-mask-jekyll-theme'
../haini.sh/haini.sh 'yarn '
sysctl: cannot stat /proc/sys/kernel/unprivileged_userns_clone: No existe el fichero o el directorio
../haini.sh/haini.sh: línea 24: test: : se esperaba una expresión entera
Tip: Usá `export PATH=/home/librenauta/0xacab/sutty/haini.sh:$PATH` para poder correr comandos de haini.sh con solo 'haini.sh'
> yarn 
yarn install v1.22.10
[1/4] Resolving packages...
success Already up-to-date.
Done in 2.01s.
make[2]: *** [Makefile:46: hain] Error 1
make[2]: se sale del directorio '/home/librenauta/0xacab/sutty/behind-the-mask-jekyll-theme'
make[1]: *** [Makefile:52: yarn] Error 2
make[1]: se sale del directorio '/home/librenauta/0xacab/sutty/behind-the-mask-jekyll-theme'
make: *** [Makefile:96: node_modules] Error 2