gnu: libmygpo-qt: Switch to Qt6.

* gnu/packages/gpodder.scm (libmygpo-qt)[inputs]: Replace qtbase-5 with qtbase.
[arguments]<configure-flags>: New argument.
(libmygpo-qt5): Inherit from libmygpo-qt.
* gnu/packages/music.scm (clementine)[inputs]: Replace libmygpo-qt with
libmygpo-qt5.

gnu/packages/gpodder.scm

@@ -141,9 +141,11 @@ locally for later listening.")
     (native-inputs
      (list pkg-config))
     (inputs
-     (list qtbase-5))
+     (list qtbase))
     (arguments
-     (list #:phases
+     (list #:configure-flags
+           #~(list "-DBUILD_WITH_QT6=ON")
+           #:phases
            #~(modify-phases %standard-phases
                (replace 'check
                  (lambda* (#:key tests? #:allow-other-keys)
@@ -158,6 +160,17 @@ locally for later listening.")
 and track podcasts.")
     (license license:lgpl2.1+)))
 
+(define-public libmygpo-qt5
+  (package/inherit libmygpo-qt
+    (name "libmygpo-qt5")
+    (inputs
+     (modify-inputs (package-inputs libmygpo-qt)
+       (replace "qtbase" qtbase-5)))
+    (arguments
+     (substitute-keyword-arguments (package-arguments libmygpo-qt)
+       ((#:configure-flags flags)
+        #~(delete "-DBUILD_WITH_QT6=ON" #$flags))))))
+
 (define-public python-mygpoclient
   (package
     (name "python-mygpoclient")

gnu/packages/music.scm

@@ -587,7 +587,7 @@ enables iPod support in music players such as Clementine.")
              gst-plugins-good
              gst-libav
              libcdio
-             libmygpo-qt
+             libmygpo-qt5
              libgpod
              libmtp
              libxml2