Attached working proof of concept with LabVIEW CLI, To make it work:
Disable Error message on logger instance (FGV in C:\Program Files (x86)\National Instruments\Shared\LabVIEW CLI\Operations\Utilities\Logger)
Enable multiple instances of LabVIEW
Spawn few labview processes that will run Builder.vi and pass instance parameter eg \..\..\Labview.exe \..\..\Builder.vi -- 1
Copy ExecuteBuildSpecAsync_class folder to C:\Program Files (x86)\National Instruments\Shared\LabVIEW CLI\Operations
Start it the same way from labview CLI but use ExecuteBuildSpecAsync insstead of ExecuteBuildSpec, should compile on free running builder or throw exception
builder.zip