[Toybox] FreeBSD porting, removing bashisms

[Ed Maste]

On Tue, 8 Jan 2019 at 15:17, Ed Maste <emaste at freebsd.org> wrote:
>
> With those changes these POSIX toys will build:
ln should also be in the POSIX list - was excluded accidentally.

>From the "other" toys I can enable:
acpi ascii base64 bunzip2 bzcat chroot chrt chvt clear count dos2unix
unix2dos factor fallocate flock fmt fsync help help_extras hexedit
lsmod lspci lspci_text lsusb makedevs mkpasswd mkswap modinfo
mountpoint pmap printenv pwdx readlink realpath reset rev setsid shred
sysctl tac timeout truncate usleep uuidgen vmstat w watch which xxd
yes

>From lsb:
hostname killall mknod mktemp pidof seq sync