Update alpine to 3.21.3 from 3.20.3

Release notes https://alpinelinux.org/posts/Alpine-3.21.3-released.html

Remove xavs2 for now as it seems unmaintained and has problems with newer
gcc version default -Wall. If someone wants it i guess we could figure out
how to fix or disable the errors.

Author: bump

Dockerfile

@@ -1,6 +1,6 @@
 # bump: alpine /ALPINE_VERSION=alpine:([\d.]+)/ docker:alpine|^3
 # bump: alpine link "Release notes" https://alpinelinux.org/posts/Alpine-$LATEST-released.html
-ARG ALPINE_VERSION=alpine:3.20.3
+ARG ALPINE_VERSION=alpine:3.21.3
 FROM $ALPINE_VERSION AS builder
 
 # Alpine Package Keeper options
@@ -904,11 +904,13 @@ ARG XAVS2_VERSION=1.4
 ARG XAVS2_URL="https://github.com/pkuvcl/xavs2/archive/refs/tags/$XAVS2_VERSION.tar.gz"
 ARG XAVS2_SHA256=1e6d731cd64cb2a8940a0a3fd24f9c2ac3bb39357d802432a47bc20bad52c6ce
 # TODO: seems to be issues with asm on musl
+# TODO: -Wno-incompatible-pointer-types need as modern gcc errors on it
 RUN \
   wget $WGET_OPTS -O xavs2.tar.gz "$XAVS2_URL" && \
   echo "$XAVS2_SHA256  xavs2.tar.gz" | sha256sum -c - && \
   tar $TAR_OPTS xavs2.tar.gz && cd xavs2-*/build/linux && \
   ./configure \
+    --extra-cflags="-Wno-incompatible-pointer-types" \
     --disable-asm \
     --enable-pic \
     --disable-cli && \