1603 - Unknown Concurrency Group '%s'.
Description
    
Concurrency Groups must be defined in Settings() before being referenced
by build steps using them.
    
Example
    
Config:
    Exec()
{
    .ConcurrencyGroupName = 'deploy'
    .ExecExecutable = 'deploy.exe'
    .ExecOutput     = 'deploy.log'
}
Output:
C:\Test\fbuild.bff(1,1): FASTBuild Error #1603 - Exec() - Unknown Concurrency Group 'deploy'.
Exec()
^
\--here
Fix:
Settings
{
    .DeployGroup = 
    [
        .ConcurrencyGroupName   = 'deploy'
        .ConcurrencyJobLimit    = 1
    ]
    .ConcurrencyGroups = { .DeployGroup }
}
Exec()
{
    .ConcurrencyGroupName = 'deploy'
    .ExecExecutable = 'deploy.exe'
    .ExecOutput     = 'deploy.log'
}
    