There is an updated pull request by amak79 against master on the void-packages repository

https://github.com/amak79/void-packages retroarch
https://github.com/void-linux/void-packages/pull/24190

retroarch: update to 1.9.0
- Use system flac, glslang, mbedtls, miniupnpc and zlib.
- Add `libHLSL.so` to `common/shlibs`. Needed when building with system glslang.
- Add patch for missing include on musl libc.
- Add patch for conflicting types build error.
- Add `wayland` build option.
- Use common build options for all platforms.
- Remove `libxml2-devel` dependency. It was removed by upstream: https://github.com/libretro/RetroArch/pull/8486

A patch file from https://github.com/void-linux/void-packages/pull/24190.patch is attached