Fix babel-standalone for realz (#6137)

* Fix babel-standalone

* Fix infinite loop in Makefile (oops)

* Override Node.js module resolution to handle babel-core

packages/babel-standalone/src/overrideModuleResolution.js

@@ -0,0 +1,24 @@
+/**
+ * babel-loader causes problems as it's not part of the monorepo. It pulls in
+ * an older version of babel-core (the version referenced by the root
+ * package.json), rather than the version of babel-core that's in the repo. The
+ * only way to solve this without moving babel-loader into the monorepo is to
+ * override Node's module resolution algorithm to specify a custom resolver for
+ * babel-core to *force* it to use our version.
+ *
+ * Here be dragons.
+ */
+
+const Module = require("module");
+
+module.exports = function overrideModuleResolution() {
+  const originalLoader = Module._load.bind(Module);
+
+  Module._load = function babelStandaloneLoader(request, parent, isMain) {
+    // Redirect babel-core to version in the repo.
+    if (request === "babel-core") {
+      request = __dirname + "/../../babel-core";
+    }
+    return originalLoader(request, parent, isMain);
+  };
+};