Allow running external function before 'bundle install'

External actions may use setup-ruby, and some actions make changes/additions to the build environment. These may be needed for dependencies.

Hence, allow those external actions to run code before 'bundle install'. This is done by passing a function as a parameter to setupRuby().

index.js

@@ -16,14 +16,14 @@ const inputDefaults = {
 // entry point when this action is run on its own
 export async function run() {
   try {
-    await setupRuby({})
+    await setupRuby()
   } catch (error) {
     core.setFailed(error.message)
   }
 }
 
 // entry point when this action is run from other actions
-export async function setupRuby(options) {
+export async function setupRuby(options = {}) {
   const inputs = { ...options }
   for (const key in inputDefaults) {
     if (!inputs.hasOwnProperty(key)) {
@@ -52,6 +52,13 @@ export async function setupRuby(options) {
 
   setupPath(newPathEntries)
 
+  // When setup-ruby is used by other actions, this allows code in them to run
+  // before 'bundle install'.  Installed dependencies may require additional
+  // libraries & headers, build tools, etc.
+  if (inputs['afterSetupPathHook'] instanceof Function) {
+    await inputs['afterSetupPathHook']({ platform, rubyPrefix, engine, version })
+  }
+
   if (inputs['bundler'] !== 'none') {
     await common.measure('Installing Bundler', async () =>
       installBundler(inputs['bundler'], platform, rubyPrefix, engine, version))