add gspell package (#3174)

remove unnecessary checks for on_fetch

packages/g/gspell/xmake.lua

@@ -0,0 +1,12 @@
+package("gspell")
+
+    set_homepage("https://gitlab.gnome.org/GNOME/gspell")
+    set_description("A spell-checking library for GTK applications")
+    set_license("LGPL-2.0-or-later")
+
+    on_fetch("linux", function (package, opt)
+        if opt.system and package.find_package then
+            return package:find_package("pkgconfig::gspell")
+        end
+    end)
+

packages/g/gtk+3/xmake.lua

@@ -4,11 +4,9 @@ package("gtk+3")
     set_description("Toolkit for creating graphical user interfaces")
     set_license("LGPL-2.0-or-later")
 
-    if on_fetch then
-        on_fetch("linux", function (package, opt)
-            if opt.system and package.find_package then
-                return package:find_package("pkgconfig::gtk+-3.0")
-            end
-        end)
-    end
+    on_fetch("linux", function (package, opt)
+        if opt.system and package.find_package then
+            return package:find_package("pkgconfig::gtk+-3.0")
+        end
+    end)