dev-qt/qtwebengine: preemptively add := to libxml2 in live

Just so it's propagated when do bumps and reduce amount of revbumps
needed later (given qtwebengine is a huge package), it will be needed
whenever libxml2-2.14 is added & keyworded/unmasked with a new soname.

Signed-off-by: Ionen Wolkens <ionen@gentoo.org>

dev-qt/qtwebengine/qtwebengine-6.9.9999.ebuild

@@ -33,7 +33,7 @@ RDEPEND="
 	app-arch/snappy:=
 	dev-libs/expat
 	dev-libs/libevent:=
-	dev-libs/libxml2[icu]
+	dev-libs/libxml2:=[icu]
 	dev-libs/libxslt
 	dev-libs/nspr
 	dev-libs/nss

dev-qt/qtwebengine/qtwebengine-6.9999.ebuild

@@ -33,7 +33,7 @@ RDEPEND="
 	app-arch/snappy:=
 	dev-libs/expat
 	dev-libs/libevent:=
-	dev-libs/libxml2[icu]
+	dev-libs/libxml2:=[icu]
 	dev-libs/libxslt
 	dev-libs/nspr
 	dev-libs/nss