www/kf5-kjs: unbreak after 020693c1

-- Could NOT find Perl (missing: PERL_EXECUTABLE)
[...]
-- The following REQUIRED packages have not been found:

 * Perl, <http://www.perl.org>
   Needed for building kdelibs

CMake Error at /usr/local/share/cmake/Modules/FeatureSummary.cmake:464 (message):
  feature_summary() Error: REQUIRED package(s) are missing, aborting CMake
  run.
Call Stack (most recent call first):
  CMakeLists.txt:88 (feature_summary)

PR:		266007

www/kf5-kjs/Makefile

@@ -7,8 +7,9 @@ COMMENT=	KF5 library providing an ECMAScript interpreter
 
 LIB_DEPENDS=	libpcre.so:devel/pcre
 
-USES=		cmake compiler:c++11-lib kde:5 pkgconfig qt:5 tar:xz
+USES=		cmake compiler:c++11-lib kde:5 perl5 pkgconfig qt:5 tar:xz
 USE_KDE=	doctools:build ecm:build
+USE_PERL5=	build
 USE_QT=		core \
 		buildtools:build qmake:build