sci-calculators/qalculate-gtk: Add optfeature for sci-libs/libqalculate[gnuplot]

Closes: https://bugs.gentoo.org/939748
Signed-off-by: Christopher Fore <csfore@posteo.net>
Signed-off-by: Andrew Ammerlaan <andrewammerlaan@gentoo.org>

sci-calculators/qalculate-gtk/qalculate-gtk-5.3.0.ebuild

@@ -5,7 +5,7 @@ EAPI=8
 
 # Note: bump with sci-libs/libqalculate and sci-calculators/qalculate-qt!
 
-inherit xdg
+inherit optfeature xdg
 
 DESCRIPTION="Modern multi-purpose calculator"
 HOMEPAGE="https://qalculate.github.io/"
@@ -37,3 +37,9 @@ src_prepare() {
 
 	default
 }
+
+pkg_postinst() {
+	xdg_pkg_postinst
+
+	optfeature "gnuplot support" sci-libs/libqalculate[gnuplot]
+}