Since 5.9, qmake is used to install files. It preserves the permissions set for a file. However, older releases used install command that explicitly set permissions to 755 for executables and 644 for other files.

Result now is that the user has to configure umask properly to make sure the permissions of files produced by the compiler make sense.

In makefiles from older qmake:

INSTALL_FILE  = install -m 644 -p
INSTALL_PROGRAM = install -m 755 -p