The `execline-umask` program

execline-umask sets the umask (file creation mask), then executes a program.

Interface

     execline-umask mask prog...

execline-umask sets the current umask to mask, then execs into prog....

By default, at execline installation time, a umask symbolic link is created, pointing to execline-umask.
When execline has been configured with the --enable-pedantic-posix option, the umask symbolic link points to the posix-umask binary instead.
Existing execline scripts calling umask will keep working no matter the chosen configuration.