sunos : fix starting errors on SunOS

Make use of XPG4 binaries on SunOS. This will fix the
following errors :

```shell
grep: illegal option -- E
Usage: grep [-c|-l|-q] [-r|-R] -hbnsviw pattern file . . .
grep: illegal option -- E
Usage: grep [-c|-l|-q] [-r|-R] -hbnsviw pattern file . . .
sh: line 335: whoami: not found
sh[335]: [: argument expected
```