LDC cross-module-inlining

[Per Nordlöw via Digitalmars-d-learn]

Is cross-module-inlining enabled by default in LDC when compiling 
in release mode or do I have to use explicitly flag for it? I 
can't find any such flag from the output of neither

    ldc2 -h
nor

    ldmd2 -h

.

Johan Engelen mentioned this, then experimental, flag in his 
DConf talk from 2017 [1]

[1] https://www.youtube.com/watch?v=IZY67TBZ0V4