In include/QtCore/qcompilerdetection.h there is following part of the code:

# if __has_include(<version>) /* remove this check once Integrity, QNX have caught up */.
# include <version>.
# endif.

This leads to problems with compiler if there is a file named VERSION in application sources (to indicate the version number of application). That check seems to be QNX and Integrity specific so it should not enter there when compiling for other platforms. Therefore that preprocessor code path should be protected.

Way to reproduce:

Compile the attached example (tested on Windows) against Qt 6.4.2
Compilation will fail with different compiler errors.

As a workaround, splitting the include paths and non-include files in source hierarchy fixes the issue.