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/reuse-dependency/output.js

@@ -0,0 +1,6 @@
+function _$_reuseDependency_main() { return _$_reuseDependency_dependency(); }
+
+function _$_reuseDependency_dependency() { 0; }
+
+_$_reuseDependency_main;
+_$_reuseDependency_dependency;