gnu: Add qt5compat.

* gnu/packages/qt.scm (qt5compat): New variable.

gnu/packages/qt.scm

@@ -831,6 +831,35 @@ (define-public qtbase
             (variable "XDG_CONFIG_DIRS")
             (files '("etc/xdg")))))))
 
+(define-public qt5compat
+  (package
+    (name "qt5compat")
+    (version "6.3.1")
+    (source (origin
+              (method url-fetch)
+              (uri (qt5-urls name version))
+              (sha256
+               (base32
+                "1zbcaswpl79ixcxzj85qzjq73962s4c7316pibwfrskqswmwcgm4"))))
+    (build-system cmake-build-system)
+    (arguments
+     (list
+      #:configure-flags #~(list "-DQT_BUILD_TESTS=ON")
+      #:phases #~(modify-phases %standard-phases
+                   (add-after 'install 'delete-installed-tests
+                     (lambda _
+                       (delete-file-recursively
+                        (string-append #$output "/tests")))))))
+    (native-inputs (list perl))
+    (inputs (list icu4c libxkbcommon qtbase qtdeclarative qtshadertools))
+    (home-page (package-home-page qtbase))
+    (synopsis "Legacy Qt 5 APIs ported to Qt 6")
+    (description "The @code{qt5compat} package includes application
+programming interfaces (APIs) from Qt 5 that were ported to Qt 6, to ease
+migration.  It provides for example the @code{GraphicalEffects} module that
+came with the @{qtgraphicaleffects} Qt 5 package.")
+    (license (list license:gpl2+ license:lgpl3+)))) ;dual licensed
+
 (define-public qtsvg-5
   (package
     (inherit qtbase-5)