nx build app watch mode doesn't work when using incremental

Question

Title says pretty much it.

I followed steps from this official nx Incremental Build Angular guide on how to use the buildLibsFromSource flag, but it only refers to the "nx serve" command.
I have to use "nx build" instead and was able to run it but when I change something in one of my libraries, build is not triggered. Other official resource does not really help on this neither.

Anyone has insights on this ?