Add fizzy-wasi tool

[axic]

TODO:

• fix ProjectUVWASI because it doesn't properly link in libuv (on macos at least)
• add FIZZY_WASI cmake option
• implement fd_write (add memory translation helpers)
• maybe restructure to make error handling nicer
• change from wasi_unstable to wasi_snapshot_preview1
• add CI task running helloworld.wasm and expect "hello world\n" on cout

Optional: support helloworld from rust

• wasi_snapshot_preview1::fd_prestat_dir_name (dummy)
• wasi_snapshot_preview1::fd_prestat_get
• wasi_snapshot_preview1::environ_sizes_get
• wasi_snapshot_preview1::environ_get (dummy)

Use hello world from https://github.com/bytecodealliance/wasmtime/blob/master/docs/WASI-tutorial.md#web-assembly-text-example as test.

Also supports running hello world generated by Rust (using wasilibc).

Spec explanation: https://github.com/WebAssembly/WASI/blob/master/phases/README.md

[axic]

@chfast @gumb0 so should we create a wasi directory or a tools/wasi directory? (Anticipating there may be another runner tool in the future.)

[axic]

There seems to be a linking error:

/usr/bin/ld: cannot find -luv

[axic]

Need to double check the spec whether we return error code here or trpa.

[chfast]

Suggested change

	uvwasi_t state;
	uvwasi_t state;
	std::unique_ptr<uvwasi_t, decltype(&uvwasi_destroy)> state_destroyer{&state, &uvwasi_destroy};

[chfast]

The idea how to test at least some aspects of WASI.
In uvwasi_options_t you can set file descriptions to previously created memory buffers (probably requires POSIX/OS-specific API). This allows providing input and checkout output in unittests.

Although, I'm still ok with merging this in the current from, and leave more extensive testing to some other day.

[axic]

@chfast your magic does not compile:

FAILED: tools/wasi/CMakeFiles/fizzy-wasi.dir/wasi.cpp.o 
/usr/bin/cmake -E __run_co_compile --tidy="clang-tidy;--extra-arg-before=--driver-mode=g++" --source=/home/builder/project/tools/wasi/wasi.cpp -- /usr/bin/clang++  -I/home/builder/project/lib/fizzy -I/home/builder/project/include -isystem _deps/src/uvwasi/include -isystem _deps/src/uvwasi-build -g -Wpedantic -Werror -Wall -Wextra -Wshadow -Wconversion -Wsign-conversion -Wno-unknown-pragmas -fstack-protector-strong -Wimplicit-fallthrough -Wcast-qual -Wcast-align -Wmissing-declarations -Wextra-semi -Wold-style-cast -Wfinal-dtor-non-final-class -Wnewline-eof -Wunreachable-code-break -Wduplicate-enum -Weverything -Wno-c++98-compat -Wno-c++98-compat-pedantic -Wno-covered-switch-default -Wno-double-promotion -Wno-float-equal -Wno-padded -Wno-switch-enum -std=c++17 -MD -MT tools/wasi/CMakeFiles/fizzy-wasi.dir/wasi.cpp.o -MF tools/wasi/CMakeFiles/fizzy-wasi.dir/wasi.cpp.o.d -o tools/wasi/CMakeFiles/fizzy-wasi.dir/wasi.cpp.o -c /home/builder/project/tools/wasi/wasi.cpp
/home/builder/project/tools/wasi/wasi.cpp:18:54: error: declaration requires an exit-time destructor [clang-diagnostic-exit-time-destructors,-warnings-as-errors]
std::unique_ptr<uvwasi_t, decltype(&uvwasi_destroy)> state_destroyer{&state, &uvwasi_destroy};
                                                     ^
/home/builder/project/tools/wasi/wasi.cpp:18:54: error: declaration requires a global destructor [clang-diagnostic-global-constructors,-warnings-as-errors]
1135 warnings generated.
Suppressed 1133 warnings (1133 in non-user code).
Use -header-filter=.* to display errors from all non-system headers. Use -system-headers to display errors from system headers as well.
2 warnings treated as errors

[axic]

Why is this const stuff so important on this?

[chfast]

The const should be the default.

[axic]

Should protest C++ to follow Rust with making const-by-default and have a mutable specifier on others :)

[chfast]

We both know this is not possible.