For multi configuration generators AUTOMOC generates the
moc files that are included in `mocs_compilation.cpp`
in `AUTOGEN_BUILD_DIR/include_$<CONFIG>/`. By doing so each
configuration reads different moc files when compiling
`mocs_compilation.cpp`. Since we do not (need to) rewrite
`mocs_compilation.cpp` on a configuration change anymore,
the files also does not need to be recompiled anymore.
Not having to rewrite and recompile `mocs_compilation.cpp`
on a configuration change anymore was the main objective of
this patch.
In a similar fashion AUTORCC generates a `qrc_BASE_CMAKE.cpp`
file below `AUTOGEN_BUILD_DIR/include_$<CONFIG>/` and
`qrc_BASE.cpp` becomes a mere wrapper that includes this
actuall rcc output file (when using multi configuration
generators).
The template files `Modules/AutoRccInfo.cmake.in` and
`Modules/AutogenInfo.cmake.in` were removed in favor
of writing the info `.cmake` files manually.
Closes#17230
This introduces concurrent thread processing in the `_autogen`
target wich processes AUTOMOC and AUTOUIC.
Source file parsing is distributed among the threads by
using a job queue from which the threads pull new parse jobs.
Each thread might start an independent ``moc`` or ``uic`` process.
Altogether this roughly speeds up the AUTOMOC and AUTOUIC build
process by the number of physical CPUs on the host system.
The exact number of threads to start in the `_autogen` target
is controlled by the new AUTOGEN_PARALLEL target property which
is initialized by the new CMAKE_AUTOGEN_PARALLEL variable.
If AUTOGEN_PARALLEL is empty or unset (which is the default)
the thread count is set to the number of physical CPUs on
the host system.
The AUTOMOC/AUTOUIC generator and the AUTORCC generator are
refactored to use a libuv loop internally.
Closes#17422.
