security/lxqt-openssh-askpass: unbreak after 020693c1

CMake Error at /usr/local/share/cmake/Modules/FindPackageHandleStandardArgs.cmake:230 (message):
  Could NOT find Perl (missing: PERL_EXECUTABLE)

PR:		266007
Reported by:	antoine (via exp-run)

security/lxqt-openssh-askpass/Makefile

@@ -10,7 +10,8 @@ WWW=		https://lxqt-project.org
 LICENSE=	LGPL21+
 
 USES=	cmake compiler:c++11-lang gettext-runtime kde:5 lxqt \
-	pkgconfig qt:5 tar:xz gnome xorg
+	perl5 pkgconfig qt:5 tar:xz gnome xorg
+USE_PERL5=	build
 USE_QT=	buildtools:build qmake:build core dbus gui linguisttools \
 	svg widgets x11extras xml
 USE_KDE=	windowsystem