Add dev-qt from an older version of the gentoo repo

Qt5 has been removed, we restore it since we still use it.

dev-qt/qttest/qttest-5.15.16.ebuild

@@ -0,0 +1,33 @@
+# Copyright 1999-2024 Gentoo Authors
+# Distributed under the terms of the GNU General Public License v2
+
+EAPI=8
+
+if [[ ${PV} != *9999* ]]; then
+	QT5_KDEPATCHSET_REV=1
+	KEYWORDS="amd64 arm arm64 ~hppa ~loong ppc ppc64 ~riscv x86"
+fi
+
+QT5_MODULE="qtbase"
+VIRTUALX_REQUIRED="test"
+inherit qt5-build
+
+DESCRIPTION="Unit testing library for the Qt5 framework"
+
+IUSE=""
+
+RDEPEND="=dev-qt/qtcore-${QT5_PV}*:5="
+DEPEND="${RDEPEND}
+	test? (
+		=dev-qt/qtgui-${QT5_PV}*
+		=dev-qt/qtxml-${QT5_PV}*
+	)
+"
+
+QT5_TARGET_SUBDIRS=(
+	src/testlib
+)
+
+QT5_GENTOO_PRIVATE_CONFIG=(
+	:testlib
+)