don't cache dump task if api dir is invalid

Author: aSemy

modules/bcv-gradle-plugin/src/main/kotlin/tasks/BCVApiDumpTask.kt

@@ -34,17 +34,26 @@ constructor(
       "subproject '${project.path}'"
     }
 
+  init {
+    outputs.cacheIf { task ->
+      require(task is BCVApiDumpTask)
+      task.validateApiDir()
+    }
+  }
+
   @TaskAction
   fun action() {
-    validateApiDir()
+    validateApiDir { msg -> error(msg) }
     updateDumpDir()
   }
 
-  private fun validateApiDir() {
+  private fun validateApiDir(ifInvalid: (msg: String) -> Unit = {}): Boolean {
     val projectDir = layout.projectDirectory.asFile.toPath().toAbsolutePath().normalize()
     val apiDir = projectDir.resolve(apiDirectory.get().asFile.toPath()).normalize()
-    require(apiDir.startsWith(projectDir)) {
-      /* language=text */ """
+    val valid = apiDir.startsWith(projectDir)
+    if (!valid) {
+      ifInvalid(
+        /* language=text */ """
         |Error: Invalid output apiDirectory
         |
         |apiDirectory is set to a custom directory, outside of the current project directory.
@@ -55,7 +64,9 @@ constructor(
         |Project directory: ${projectDir.invariantSeparatorsPathString}
         |apiDirectory:      ${apiDir.invariantSeparatorsPathString}
       """.trimMargin()
+      )
     }
+    return valid
   }
 
   private fun updateDumpDir() {