gst-plugins-bad1: add libopenal-devel to build dependencies (#4979)

gst-plugins-bad1 needs to be built against libopenal to enable
the building of openalsink which is required by applications like
clementine if phonon-backend-gstreamer is used.

srcpkgs/gst-plugins-bad1/template

@@ -2,7 +2,7 @@
 pkgname=gst-plugins-bad1
 reverts="1:1.4.5_6"
 version=1.8.3
-revision=2
+revision=3
 wrksrc="${pkgname/1/}-${version#*:}"
 lib32disabled=yes
 build_style=gnu-configure
@@ -15,7 +15,7 @@ makedepends="alsa-lib-devel celt-devel libressl-devel exempi-devel
  xvidcore-devel jasper-devel libmodplug-devel neon-devel libcurl-devel
  libvpx-devel libvdpau-devel libgsm-devel librtmp-devel libass-devel
  mpg123-devel soundtouch-devel opus-devel libwebp-devel wayland-devel
- libsrtp-devel"
+ libsrtp-devel libopenal-devel"
 depends="gst-plugins-base1>=${version}"
 short_desc="GStreamer plugins from the bad set (v1.x)"
 maintainer="Juan RP <xtraeme@voidlinux.eu>"