PiCore 13.x SDL2_mixer 2.6.2:

From:
https://www.libsdl.org/projects/SDL_mixer/release/SDL2_mixer-2.6.2.tar.gz

Based on x86_64 extension:
http://tinycorelinux.net/10.x/x86_64/tcz/src/sdl2_mixer/compile_sdl2_mixer

* Install extensions: compiletc sdl2-dev mpg123-dev opusfile-dev squashfs-tools liblz4
* export CFLAGS="-flto -Os -pipe" CXXFLAGS="-flto -Os -pipe -fno-exceptions -fno-rtti" LDFLAGS="-Wl,-O1"
* ./configure --prefix=/usr/local --localstatedir=/var --enable-music-mp3-mpg123
* make
* src/sdl2_mixer

* touch /tmp/mark
* sudo make DESTDIR=/tmp/sdl2_mixer install
* split /tmp/sdl2_mixer into directories: sdl2_mixer sdl2_mixer-dev

* sudo chown -R root:root sdl2_mixer*
* sudo strip sdl2_mixer/usr/local/lib/libSDL2_mixer-2.0.so.0.600.2
* In each dir. run "find usr ! -type d | sed "s/^/\//g" > ../sdl2_mixer.tcz.list".
 - for dir in `find -maxdepth 1 -mindepth 1 -type d`; do cd $dir; find usr ! -type d | sed "s/^/\//g" > ../$dir.tcz.list; cd ..; done
* sudo chown -R root:root *
* Make into extensions using mksquashfs. "mksquashfs sdl2_mixer sdl2_mixer.tcz
  "md5sum sdl2_mixer.tcz > sdl2_mixer.tcz.md5.txt" etc...
 - for dir in `find -maxdepth 1 -mindepth 1 -type d`; do mksquashfs $dir ${dir#./}.tcz; md5sum ${dir#./}.tcz > ${dir#./}.tcz.md5.txt; done
* Make sdl2_mixer.tcz.dep:

$ ldd /tmp/sdl2_mixer/usr/local/lib/libSDL2_mixer-2.0.so.0.600.2

Deps:
sdl2_mixer.tcz.dep
 SDL2.tcz
sdl2_mixer-dev.tcz.dep
 sdl2_mixer.tcz
 sdl2-dev.tcz
 mpg123-dev.tcz
 opusfile-dev.tcz


* Copy sdl2_mixer.tcz (+ dep, md5) to "tce/optional".
* tce-load -i sdl2_mixer