Cannot configure CMake project in Terminal

The bottom line is that I cannot configure a CMake-based Qt project in Creator's terminal which works fine in gnome-terminal. Since this doesn't happen with all builds of Qt and I cannot know what makes the significant difference, I'm posting instructions how to get into the situation I am in.

1. Clone qt5.git's dev branch.
   I have it at 8f108aab07e4d2b5b8022e98ffa5433029e08269
2. In that, initialize qtbase only:
   perl init-repository --module-subset=qtbase
3. In a separate directory, configure those sources for fuzzing with UBSAN and build them:
   /mnt/qt-bisect/qt5/configure -platform linux-clang -opensource -confirm-license -no-widgets -prefix $PWD/qtbase -release -static -no-gc-binaries -sanitize fuzzer-no-link -sanitize undefined -qt-tiff && nice cmake --build .
   I attached config.opt and config.summary from this build.
4. Start Creator with empty settings (-tcs).
   I used Creator from the Online Installer.
5. Open Creator's built-in Terminal (Alt+5)
6. From that Terminal, in yet another separate directory, try configuring (qt-cmake) a fuzzer from the sources you prepared in steps 1 and 2:
   CXX=clang++ /mnt/qt-bisect/build/qtbase/bin/qt-cmake /mnt/qt-bisect/qt5/qtbase/tests/libfuzzer/gui/image/qimage/loadfromdata/
   Expected: The build succeeds, as it does in gnome-terminal.
   Actual: Configuring fails:

   -- The CXX compiler identification is Clang 19.1.7
   -- Detecting CXX compiler ABI info
   -- Detecting CXX compiler ABI info - done
   -- Check for working CXX compiler: /bin/clang++ - skipped
   -- Detecting CXX compile features
   -- Detecting CXX compile features - done
   -- Performing Test CMAKE_HAVE_LIBC_PTHREAD
   -- Performing Test CMAKE_HAVE_LIBC_PTHREAD - Success
   -- Found Threads: TRUE
   -- Found ZLIB: /usr/lib/libz.so (found version "1.3.1")
   -- Found WrapSystemZLIB: TRUE (found version "1.3.1")
   -- Using system ZLIB.
   -- Found WrapZLIB: TRUE (found version "1.3.1")
   -- Performing Test HAVE_STDATOMIC
   -- Performing Test HAVE_STDATOMIC - Success
   -- Found WrapAtomic: TRUE
   -- Looking for backtrace
   -- Looking for backtrace - found
   -- backtrace facility detected in default set of libraries
   -- Found Backtrace: /usr/include
   -- Found WrapSystemDoubleConversion: /lib/cmake/double-conversion/double-conversionConfig.cmake (found version "3.3.0")
   -- Checking for module 'libb2'
   --   Found libb2, version 0.98.1
   -- Found ICU: /usr/include (found suitable version "76.1", minimum required is "50.1") found components: i18n uc data
   -- Found WrapSystemPCRE2: /usr/lib/libpcre2-16.so (found version "10.45")
   -- Using system PCRE2.
   -- Found WrapPCRE2: TRUE (found version "10.45")
   -- Found WrapZSTD: 1.5.7 (found suitable version "1.5.7", minimum required is "1.3")
   -- Found GLIB2: /usr/lib/libglib-2.0.so
   -- Performing Test HAVE_GETTIME
   -- Performing Test HAVE_GETTIME - Success
   -- Performing Test HAVE_SHM_OPEN_SHM_UNLINK
   -- Performing Test HAVE_SHM_OPEN_SHM_UNLINK - Success
   -- Found WrapRt: TRUE
   -- Found OpenGL: /usr/lib/libOpenGL.so
   -- Found WrapOpenGL: TRUE
   -- Performing Test HAVE_EGL
   -- Performing Test HAVE_EGL - Success
   -- Found EGL: /usr/include (found version "1.5")
   -- Found WrapSystemPNG: /usr/lib/libpng.so;/usr/lib/libz.so (found version "1.6.47")
   -- Using system PNG.
   -- Found WrapPNG: TRUE (found version "1.6.47")
   CMake Error at /lib/cmake/harfbuzz/harfbuzz-config.cmake:7 (message):
     File or directory //include/harfbuzz referenced by variable
     HARFBUZZ_INCLUDE_DIR does not exist !
   Call Stack (most recent call first):
     /lib/cmake/harfbuzz/harfbuzz-config.cmake:22 (set_and_check)
     /mnt/qt-bisect/build/qtbase/lib/cmake/Qt6/FindWrapSystemHarfbuzz.cmake:12 (find_package)
     /mnt/qt-bisect/build/qtbase/lib/cmake/Qt6/QtFindWrapHelper.cmake:69 (find_package)
     /mnt/qt-bisect/build/qtbase/lib/cmake/Qt6/FindWrapHarfbuzz.cmake:6 (qt_find_package_system_or_bundled)
     /usr/share/cmake/Modules/CMakeFindDependencyMacro.cmake:76 (find_package)
     /mnt/qt-bisect/build/qtbase/lib/cmake/Qt6/QtPublicDependencyHelpers.cmake:36 (find_dependency)
     /mnt/qt-bisect/build/qtbase/lib/cmake/Qt6Gui/Qt6GuiDependencies.cmake:46 (_qt_internal_find_third_party_dependencies)
     /mnt/qt-bisect/build/qtbase/lib/cmake/Qt6Gui/Qt6GuiConfig.cmake:40 (include)
     /mnt/qt-bisect/build/qtbase/lib/cmake/Qt6/Qt6Config.cmake:223 (find_package)
     CMakeLists.txt:13 (find_package)
   
   
   CMake Warning at /mnt/qt-bisect/build/qtbase/lib/cmake/Qt6/Qt6Config.cmake:223 (find_package):
     Found package configuration file:
   
       /mnt/qt-bisect/build/qtbase/lib/cmake/Qt6Gui/Qt6GuiConfig.cmake
   
     but it set Qt6Gui_FOUND to FALSE so package "Qt6Gui" is considered to be
     NOT FOUND.
   Call Stack (most recent call first):
     CMakeLists.txt:13 (find_package)
   
   
   -- Configuring incomplete, errors occurred!
   

FWIW, I noticed that the set command shows very different environment variables in the two terminals, including a different PATH. I attached both.