dev-libs/libtsm: wire up tests

Signed-off-by: Sam James <sam@gentoo.org>

dev-libs/libtsm/libtsm-4.0.2_p20231223.ebuild

@@ -1,4 +1,4 @@
-# Copyright 1999-2024 Gentoo Authors
+# Copyright 1999-2025 Gentoo Authors
 # Distributed under the terms of the GNU General Public License v2
 
 EAPI=8
@@ -15,8 +15,18 @@ S=${WORKDIR}/${PN}-${COMMIT}
 LICENSE="LGPL-2.1 MIT"
 SLOT="0/4"
 KEYWORDS="~amd64 ~x86"
+IUSE="test"
+RESTRICT="!test? ( test )"
 
 PATCHES=(
 	"${FILESDIR}/${PN}-cmake.patch"
 	"${FILESDIR}/${PN}-clang16-static_assert-fix.patch"
 )
+
+src_configure() {
+	local mycmakeargs=(
+		-DBUILD_TESTING=$(usex test)
+	)
+
+	cmake_src_configure
+}