dev-qt/qtcore: move system-doubleconversion handling to the eclass

Gentoo-bug: 581054

dev-qt/qtcore/qtcore-5.7.1-r2.ebuild

@@ -13,8 +13,8 @@ fi
 
 IUSE="icu systemd"
 
-# TODO after bug 581054: dev-libs/double-conversion:=
 DEPEND="
+	dev-libs/double-conversion:=
 	dev-libs/glib:2
 	>=dev-libs/libpcre-8.38[pcre16,unicode]
 	>=sys-libs/zlib-1.2.5

eclass/qt5-build.eclass

@@ -564,8 +564,7 @@ qt5_base_configure() {
 		# prefer system libraries (only common hard deps here)
 		-system-zlib
 		-system-pcre
-		# TODO after bug 581054
-		#$([[ ${QT5_MINOR_VERSION} -ge 7 ]] && echo -system-doubleconversion)
+		$([[ ${QT5_MINOR_VERSION} -ge 7 ]] && echo -system-doubleconversion)
 
 		# disable everything to prevent automagic deps (part 1)
 		-no-mtdev