Add kotlin.build.disable.werror to disable -Werror locally

This can be placed, for example, in `local.properties` to temporarily
disable `-Werror` in compiler/stdlib/plugin/test modules during
development.

libraries/commonConfiguration.gradle

@@ -37,10 +37,12 @@ ext.configureJvm6Project = { Project project ->
         }
     }
 
-    project.tasks.withType(org.jetbrains.kotlin.gradle.dsl.KotlinCompile.class) { task ->
-        if (!tasksWithWarnings.contains(task.path)) {
-            task.kotlinOptions {
-                allWarningsAsErrors = true
+    if (!BuildPropertiesExtKt.getDisableWerror(project.kotlinBuildProperties)) {
+        project.tasks.withType(org.jetbrains.kotlin.gradle.dsl.KotlinCompile.class) { task ->
+            if (!tasksWithWarnings.contains(task.path)) {
+                task.kotlinOptions {
+                    allWarningsAsErrors = true
+                }
             }
         }
     }