dev-libs/cereal: conditionally skip tests

Closes: https://bugs.gentoo.org/836688
Signed-off-by: Matthew Smith <matthew@gentoo.org>

dev-libs/cereal/cereal-1.3.2-r2.ebuild

@@ -42,10 +42,10 @@ src_configure() {
 		-DSKIP_PERFORMANCE_COMPARISON=ON
 
 		-DWITH_WERROR=OFF
-
-		# TODO: Enable if multilib?
-		-DSKIP_PORTABILITY_TEST=ON
 	)
 
+	# TODO: Enable if multilib?
+	use test && mycmakeargs+=( -DSKIP_PORTABILITY_TEST=ON )
+
 	cmake_src_configure
 }