Instead of constantly trying to find packages by calling
qt_find_package on each reconfiguration, record which packages were
found during initial configuration. Then on a second reconfiguration,
skip looking for packages that were not found on the initial
configuration.
This speeds up reconfiguration on certain platforms and repos.
Here are some stats for my macOS qtbase build.
not skip 3.69s user 4.96s system 98% cpu 8.750 total
skip 2.69s user 1.00s system 97% cpu 3.792 total
Top-level build with -submodules=qtquick3d
not skip 15.03s user 10.58s system 97% cpu 26.334 total
skip 13.87s user 5.16s system 96% cpu 19.724 total
Note this is a behavior change from how find_package is used in most
CMake projects, where if a package was previously missing, the
developer can just install the package and reconfigure to pick it up.
With this change, they will first have to remove their CMakeCache.txt
file and configure from scratch, or remove the
QT_INTERNAL_PREVIOUSLY_FOUND_PACKAGES cache variable and reconfigure.
For this reason, we enable this behavior by default only in
-developer-builds.
Builders can also opt in or out by setting the
QT_INTERNAL_SAVE_PREVIOUSLY_FOUND_PACKAGES variable to either ON or
OFF.
Note this behavior does not apply to user projects, or direct
find_package calls (as opposed to qt_find_package).
Fixes: QTBUG-107251
Change-Id: Iee9c5d120eb09e2a94eebb059a2174ef6b241e03
Reviewed-by: Kai Köhne <kai.koehne@qt.io>
Reviewed-by: Amir Masoud Abdol <amir.abdol@qt.io>
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
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