libffi: support wasm32

[visualfc]

build libffi for Emscripten

// https://github.com/libffi/libffi
emconfigure ./configure --host=wasm32-unknown-emscripten --prefix=/usr/local/libffi-wasm
emmake make
emmake make install

support reflect package

PKG_CONFIG_PATH=/usr/local/libffi-wasm/lib/pkgconfig GOOS=js GOARCH=wasm llgo build -tags=nogc -o main.html .

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 86.64%. Comparing base (900ae67) to head (ce984d4).
Report is 16 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #1144   +/-   ##
=======================================
  Coverage   86.64%   86.64%           
=======================================
  Files          29       29           
  Lines        7343     7343           
=======================================
  Hits         6362     6362           
  Misses        914      914           
  Partials       67       67           

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