When i try to compile qt 5.15.2 source under Debian Buster configure create this report:

Checking for XCB Util >= 0.3.9... no

But under Debian system (all platform, also unstable branch) there only version0.3.8:

$ rmadison xcb-util

xcb-util   | 0.3.8-3       | oldoldstable   | source

xcb-util   | 0.3.8-3       | oldstable      | source

xcb-util   | 0.3.8-3       | stable         | source

xcb-util   | 0.3.8-3       | testing        | source

xcb-util   | 0.3.8-3       | unstable       | source

xcb-util   | 0.3.8-3       | unstable-debug | source