Build: enable Werror for almost all compileKotlin tasks

The only exception at this point is :kotlin-gradle-plugin:compileKotlin.

compiler/build.gradle.kts

@@ -1,4 +1,3 @@
-import org.jetbrains.kotlin.gradle.dsl.KotlinCompile
 import org.jetbrains.kotlin.ideaExt.idea
 import java.io.File
 
@@ -10,8 +9,6 @@ plugins {
 val compilerModules: Array<String> by rootProject.extra
 val otherCompilerModules = compilerModules.filter { it != path }
 
-val tasksWithWarnings: List<String> by rootProject.extra
-
 val antLauncherJar by configurations.creating
 
 dependencies {
@@ -68,18 +65,6 @@ if (kotlinBuildProperties.isInJpsBuildIdeaSync) {
     }
 }
 
-if (!kotlinBuildProperties.disableWerror) {
-    allprojects {
-        tasks.withType<KotlinCompile<*>> {
-            if (path !in tasksWithWarnings) {
-                kotlinOptions {
-                    allWarningsAsErrors = true
-                }
-            }
-        }
-    }
-}
-
 projectTest(parallel = true) {
     dependsOn(":dist")