Make sure to actually use yarn to install the main-packages, otherwise the packages.json#resolutions property will not be used and @babel/helpers would not get overruled

Overruled @babel/helpers to fix how initializers play with decorated properties. Thus circumventing the imperformant and lengthy code being generated by babel in the non-legacy option.

packages/babel-helpers/test/fixtures/dependencies/multiple/plugin.js

@@ -0,0 +1,30 @@
+const defineHelper = require("../../../helpers/define-helper").default;
+
+const dependency1 = defineHelper(__dirname, "dependency1", `
+  export default function fn() { 0; }
+`);
+
+const dependency2 = defineHelper(__dirname, "dependency2", `
+  export default function fn() { 1; }
+`);
+
+const main = defineHelper(__dirname, "main", `
+  import dep1 from "${dependency1}";
+  import dep2 from "${dependency2}";
+
+  export default function helper() {
+    return dep1() + dep2();
+  }
+`);
+
+module.exports = function() {
+  return {
+    visitor: {
+      Identifier(path) {
+        if (path.node.name !== "REPLACE_ME") return;
+        const helper = this.addHelper(main);
+        path.replaceWith(helper);
+      },
+    },
+  };
+};