Sandcat fails to start when whoami is not found

[alexanderkent]

Describe the bug
Sandcat agent fails on startup when whoami command is not found on the platform.

sandcat/gocat/agent/agent_util.go

Line 15 in e903198

if usernameBytes, err := exec.Command("whoami").CombinedOutput(); err == nil {

To Reproduce
Steps to reproduce the behavior:

1. Temp remove whoami e.g. rename, alter path etc
2. Launch sandcat agent -v

./sandcat-arm64 -v
Starting sandcat in verbose mode.
[-] Error when initializing agent: exec: "whoami": executable file not found in $PATH
[-] Exiting.

Expected behavior
Not all platforms have whoami -- soft-fail instead of a terminal error?

Desktop (please complete the following information):

• arm64 / IoT / debian