[skip ci] Add links to the build instruction

Author: kateinoigakukun

packages/npm-packages/ruby-head-wasm-emscripten/README.md

@@ -58,7 +58,7 @@ This package is a thin wrapper of Emscripten module, so you can control the beha
 
 For building the package from source, you need to prepare a Ruby build produced by Emscripten, and you need Emscripten SDK in your PATH.
 
-The instructions for building a Ruby targeting WebAssembly are available at: [TODO](./).
+The instructions for building a Ruby targeting WebAssembly are available [here](https://github.com/ruby/ruby.wasm#building-from-source).
 
 Then, you can run the following command in your shell:
 

packages/npm-packages/ruby-head-wasm-wasi/README.md

@@ -252,7 +252,7 @@ Error class thrown by Ruby execution
 
 For building the package from source, you need to prepare a Ruby build produced by WASI SDK, and you need [`wit-bindgen`](https://github.com/bytecodealliance/wit-bindgen) and [`wasm-opt`](https://github.com/webassembly/binaryen#tools) in your PATH.
 
-The instructions for building a Ruby targeting WebAssembly are available at: [TODO](./).
+The instructions for building a Ruby targeting WebAssembly are available [here](https://github.com/ruby/ruby.wasm#building-from-source).
 
 Then, you can run the following command in your shell: