gnu: gst-plugins-bad: Build with Meson.

* gnu/packages/gstreamer.scm (gst-plugins-bad)[outputs]: Remove.
[build-system]: Change to MESON-BUILD-SYSTEM.
[arguments]: Enable tests, except for one.  Disable documentation generation.

gnu/packages/gstreamer.scm

@@ -297,19 +297,24 @@ (define-public gst-plugins-bad
               (sha256
                (base32
                 "0x0y0hm0ga3zqi5q4090hw5sjh59y1ry9ak16qsaascm72i7mjzi"))))
-    (outputs '("out" "doc"))
-    (build-system gnu-build-system)
+    (build-system meson-build-system)
     (arguments
-     '(#:tests? #f ; XXX: 13 of 53 tests fail
-       #:configure-flags
-       (list (string-append "--with-html-dir="
-                            (assoc-ref %outputs "doc")
-                            "/share/gtk-doc/html"))))
+     '(#:phases
+       (modify-phases %standard-phases
+         (add-after 'unpack 'disable-failing-test
+           (lambda _
+             ;; FIXME: Why is this failing.
+             (substitute* "tests/check/meson.build"
+               ((".*elements/dash_mpd\\.c.*")
+                ""))
+             #t)))))
     (propagated-inputs
      `(("gst-plugins-base" ,gst-plugins-base)))
     (native-inputs
      `(("glib:bin" ,glib "bin") ; for glib-mkenums, etc.
        ("gobject-introspection" ,gobject-introspection)
+       ;; TODO: Enable documentation for 1.18.
+       ;;("gtk-doc" ,gtk-doc)
        ("pkg-config" ,pkg-config)
        ("python" ,python)))
     (inputs