Filesystem in userspace support (FUSE)

I wish a wasi program could emulate filesystem, e.g.:

myprogram mount ./configs
# Downloads my config files in ./configs.
# I edit configs in ./configs.
vim ./configs/main.json
# libfuse automatically uploads my changes if no errors.
# Web service starts working according to new configs without the need to visit a site
# and change configs there.
umount ./configs

I tried to compile libfuse's hello.c but get the following error in wasi-sdk:

$ /opt/wasi-sdk/bin/clang hello.c `pkg-config fuse3 --cflags --libs` -o demo.wasm
In file included from hello.c:24:
/usr/local/include/fuse3/fuse.h:25:10: fatal error: 'sys/statvfs.h' file not found
#include <sys/statvfs.h>
         ^~~~~~~~~~~~~~~
1 error generated.

Initially discussed here: https://github.com/CraneStation/wasi-sdk/issues/66.

Start with libfuse's example/hello.c and the wasi-sdk compilation command shown in the issue. Investigate the missing sys/statvfs.h dependency and the requested FUSE-style filesystem behavior for a WASI program. Done means the stated example can be compiled or the support gap is otherwise addressed, but the issue does not identify implementation files or tests.