Revert "Remove RUBY_BUILD_ROOT"

This reverts commit 919e8c7.

Author: kateinoigakukun

packages/npm-packages/ruby-wasm-wasi/test/init.js

@@ -74,7 +74,10 @@ async function initComponentRubyVM({ suppressStderr } = { suppressStderr: false
   }
   const vm = await RubyVM._instantiate(async (jsRuntime) => {
     const { cli, clocks, filesystem, io, random, sockets } = preview2Shim;
-    filesystem._setPreopens({})
+    filesystem._setPreopens({
+      "/usr": path.join(process.env.RUBY_BUILD_ROOT, "usr"),
+      "/bundle": path.join(process.env.RUBY_BUILD_ROOT, "bundle"),
+    })
     cli._setArgs(["ruby.wasm"].concat(process.argv.slice(2)));
     cli._setCwd("/")
     const root = await instantiate(getCoreModule, {

packages/npm-packages/ruby-wasm-wasi/tools/run-test-unit.mjs

@@ -39,6 +39,8 @@ const instantiateComponent = async (rootTestFile) => {
     const dirname = path.dirname(new URL(import.meta.url).pathname);
     filesystem._setPreopens({
       "/__root__": path.join(dirname, ".."),
+      "/usr": path.join(process.env.RUBY_BUILD_ROOT, "usr"),
+      "/bundle": path.join(process.env.RUBY_BUILD_ROOT, "bundle"),
     })
     cli._setArgs(["ruby.wasm"].concat(process.argv.slice(2)));
     cli._setCwd("/")