TEST_IS_INTERACTIVE=X11 vs PORTS_PRIVSEP

Hi ports@

When I run with PORTS_PRIVSEP activated, I can no longer run X11 tests,
here below is an example. Is there a workaround for this? Is this a
known issue?

Quite simply reproducible: security/keepassxc && make test


$ cd /usr/ports/pobj/plasma-framework-5.110.0/bin
$ env -i DISPLAY=:0 XAUTHORITY=/home/rsadowski/.Xauthority /usr/ports/pobj/plasma-framework-5.110.0/build-amd64/bin/plasma-sortfiltermodeltest
QStandardPaths: XDG_RUNTIME_DIR not set, defaulting to '/tmp/runtime-rsadowski'
********* Start testing of SortFilterModelTest *********
Config: Using QtTest library 5.15.10, Qt 5.15.10 (x86_64-little_endian-lp64 shared (dynamic) release build; by Clang 13.0.0 ), unknown unknown
PASS : SortFilterModelTest::initTestCase()
PASS : SortFilterModelTest::setFilterRegExp()
PASS : SortFilterModelTest::setModel()
PASS : SortFilterModelTest::setEmptyModel()
PASS : SortFilterModelTest::mapRowToSource()
PASS : SortFilterModelTest::mapRowFromSource()
PASS : SortFilterModelTest::cleanupTestCase()
Totals: 7 passed, 0 failed, 0 skipped, 0 blacklisted, 16ms
********* Finished testing of SortFilterModelTest *********


$ doas -u _pbuild env -i DISPLAY=:0 XAUTHORITY=/home/rsadowski/.Xauthority SHELL=/bin/ksh HOME="." /usr/ports/pobj/plasma-framework-5.110.0/build-amd64/bin/plasma-sortfiltermodeltest
Authorization required, but no authorization protocol specified

qt.qpa.xcb: could not connect to display :0
qt.qpa.plugin: Could not load the Qt platform plugin "xcb" in "" even though it was found.
This application failed to start because no Qt platform plugin could be initialized. Reinstalling the application may fix this problem.

Available platform plugins are: eglfs, minimal, minimalegl, offscreen, vnc, wayland-egl, wayland, wayland-xcomposite-egl, wayland-xcomposite-glx, xcb.

zsh: abort (core dumped) doas -u _pbuild env -i DISPLAY=:0 XAUTHORITY=/home/rsadowski/.Xauthority