x11/compton-conf: unbreak after 020693c

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)

x11/compton-conf/Makefile

@@ -13,8 +13,9 @@ LICENSE=	LGPL21+
 LIB_DEPENDS=	libconfig.so:devel/libconfig
 RUN_DEPENDS=	compton:x11-wm/compton
 
-USES=	cmake compiler:c++14-lang localbase:ldflags lxqt qt:5 \
+USES=	cmake compiler:c++14-lang localbase:ldflags lxqt perl5 qt:5 \
 	pkgconfig tar:xz
+USE_PERL5=	build
 USE_QT=	buildtools:build qmake:build core dbus gui linguisttools \
 	widgets
 USE_LXQT=	buildtools