Upgrade to GStreamer v1.24.0

Two notes:

1. We now have some C++ files getting built for some reason.

2. There's a warning about gst-plugin-scanner not being available due to
   our "unusual" setup. It doesn't break things since the Hypcast image
   doesn't need external plugins, but it's annoying and would be nice to
   fix in the future.

Dockerfile

@@ -6,7 +6,7 @@ ARG GOLANG_BASE=docker.io/library/golang:1.22-alpine3.19
 # The Node.js image does not require any particular OS.
 ARG NODEJS_BASE=docker.io/library/node:20-alpine
 # See https://gstreamer.freedesktop.org/download/.
-ARG GSTREAMER_VERSION=1.22.10
+ARG GSTREAMER_VERSION=1.24.0
 
 
 # Let's get the client build out of the way, since it's much simpler than
@@ -46,7 +46,7 @@ ARG TARGETARCH TARGETVARIANT
 COPY build/hypcast-buildenv.sh /hypcast-buildenv.sh
 RUN \
   source /hypcast-buildenv.sh && \
-  sysroot_init gcc libc-dev glib-dev a52dec-dev libmpeg2-dev opus-dev x264-dev
+  sysroot_init gcc libc-dev libstdc++-dev glib-dev a52dec-dev libmpeg2-dev opus-dev x264-dev
 
 
 # The GStreamer build base layer sets up parts of the GStreamer build that are
@@ -115,7 +115,7 @@ ARG TARGETARCH TARGETVARIANT
 COPY build/hypcast-buildenv.sh /hypcast-buildenv.sh
 RUN \
   source /hypcast-buildenv.sh && \
-  sysroot_init tini glib a52dec libmpeg2 opus x264-libs
+  sysroot_init tini libstdc++ glib a52dec libmpeg2 opus x264-libs
 
 
 # The final image simply assembles the results of previous build steps.