Edit: file was intentionally removed: emscripten-core/emscripten#14248

I'm attempting to update form trzeci/emscripten:1.39.6-upstream to emscripten/emsdk:3.1.3.
1.39.6 contains sendfile.h in /emsdk_portable/emscripten/sdk/system/include/libc/sys/.
3.1.3 does not contain sendfile.h in /emsdk/upstream/emscripten/cache/sysroot/include/sys/.
There are not other headers missing.

musl still ships sendfile.h https://github.com/emscripten-core/musl/tree/master/include/sys/,
however it's missing from https://github.com/emscripten-core/emscripten/tree/main/system/lib/libc/musl/include/sys/