Previously if -extprefix /tmp/sysroot (CMAKE_STAGING_PREFIX) -developer-build (FEATURE_developer_build) were specified, but -prefix (CMAKE_INSTALL_PREFIX) was not, the build system would set the CMAKE_INSTALL_PREFIX to the qtbase build dir. Then, if targeting desktop, this would be considered a non-prefix build (ninja install would refuse to work), whereas in a cross-build it would be considered an installable build. In both cases though, the rpath of installed binaries would point to the qtbase build dir (because CMAKE_INSTALL_PREFIX would be set to the qtbase build dir). This is quite confusing behavior, in more than one way. Change the build system to consider that an explicit -extprefix should cause Qt to always be installed, even if -developer-build is specified. This means the installed rpaths and on-device install prefix (CMAKE_INSTALL_PREFIX) will now use the default computed install prefix, e.g. /usr/local/Qt It also means that to get a non-installable developer + custom staging and install (on-device) prefix build, users will have to be explicit and set all the options -extprefix ~/qt/qtbase_build_dir -prefix /usr -developer-build Pick-to: 6.2 6.3 Change-Id: Ib560452a4b4778860e0fd7666c76f8a6745773ee Reviewed-by: Jörg Bornemann <joerg.bornemann@qt.io>