Update MakeReleaseNotes to crash if notes are missing. (#5613)

The task is only invoked on projects that are scheduled to be released.
And projects that publish refdocs are the ones that also publish release
notes. The task now verifies that if it's called in a project that
publishes refdocs, it has to have release notes, otherwise it breaks.

Author: rlazo

buildSrc/src/main/java/com/google/firebase/gradle/plugins/MakeReleaseNotesTask.kt

@@ -17,11 +17,13 @@
 package com.google.firebase.gradle.plugins
 
 import org.gradle.api.DefaultTask
+import org.gradle.api.GradleException
 import org.gradle.api.file.RegularFileProperty
 import org.gradle.api.tasks.InputFile
 import org.gradle.api.tasks.OutputFile
 import org.gradle.api.tasks.StopActionException
 import org.gradle.api.tasks.TaskAction
+import org.gradle.work.DisableCachingByDefault
 
 /**
  * Creates the release notes for the given project.
@@ -35,6 +37,7 @@ import org.gradle.api.tasks.TaskAction
  * changes to release
  * @see make
  */
+@DisableCachingByDefault
 abstract class MakeReleaseNotesTask : DefaultTask() {
   @get:InputFile abstract val changelogFile: RegularFileProperty
 
@@ -82,8 +85,11 @@ abstract class MakeReleaseNotesTask : DefaultTask() {
     val unreleased = changelog.releases.first()
     val version = project.version.toString()
 
+    if (!project.firebaseLibrary.publishJavadoc)
+      throw StopActionException("No release notes required for ${project.name}")
+
     if (!unreleased.hasContent())
-      throw StopActionException("No changes to release for project: ${project.name}")
+      throw GradleException("Missing release notes for \"${project.name}\"")
 
     val versionClassifier = version.replace(".", "-")