CMAKE_AUTOGEN_PARALLEL
From Get docs
Cmake/docs/3.21/variable/cmake autogen parallel
CMAKE_AUTOGEN_PARALLEL
New in version 3.11.
Number of parallel moc
or uic
processes to start when using AUTOMOC and AUTOUIC.
This variable is used to initialize the AUTOGEN_PARALLEL property on all the targets. See that target property for additional information.
By default CMAKE_AUTOGEN_PARALLEL is unset.
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https://cmake.org/cmake/help/v3.21/variable/CMAKE_AUTOGEN_PARALLEL.html