• Given: a completed qt5.git ninja build with -ccache -no-pch.
• When: a configure -redo is performed explicitly (by the user) or implicitly (by ninja noting a change in a CMakeLists.txt)
• Then: all of qtbase is rebuilt, and ccache reports zero (0) cache hits
• Expected: either nothing of qtbase is rebuilt, or at least with a 100% cache hit rate, even if only indirect (preprocessed source)

Attached is the output of ninja -d explain. First, on a ready-built build-dir (except tst_qstring.cpp and tst_qanystringview.cpp, which are expected to fail to compile), then, without changing anything in the srcdir, after a configure -redo. The log ends with ccache --print-stats showing that nothing was hitting the cache.

$ cat config.opt
-ccache
-no-pch
-opensource
-confirm-license
-release
-force-debug-info
-separate-debug-info
-c++std
c++2b
-developer-build
-skip
qtgrpc
-make
examples
--webengine-jumbo-build=31
-webengine-proprietary-codecs
-sctp
-headersclean
-qtnamespace
Qt6
--
-DQT_BUILD_EXAMPLES_BY_DEFAULT=ON