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.

build.gradle.kts

@@ -472,7 +472,7 @@ allprojects {
         }
     }
 
-    if (!kotlinBuildProperties.isInJpsBuildIdeaSync && !kotlinBuildProperties.useFir) {
+    if (!kotlinBuildProperties.isInJpsBuildIdeaSync && !kotlinBuildProperties.useFir && !kotlinBuildProperties.disableWerror) {
         // For compiler and stdlib, allWarningsAsErrors is configured in the corresponding "root" projects
         // (compiler/build.gradle.kts and libraries/commonConfiguration.gradle).
         val projectsWithWarningsAsErrors = listOf("core", "plugins").map { File(it).absoluteFile }

buildSrc/src/main/kotlin/BuildPropertiesExt.kt

@@ -18,3 +18,5 @@ val KotlinBuildProperties.proguard: Boolean get() = postProcessing && getBoolean
 val KotlinBuildProperties.jarCompression: Boolean get() = getBoolean("kotlin.build.jar.compression", isTeamcityBuild)
 
 val KotlinBuildProperties.ignoreTestFailures: Boolean get() = getBoolean("ignoreTestFailures", isTeamcityBuild)
+
+val KotlinBuildProperties.disableWerror: Boolean get() = getBoolean("kotlin.build.disable.werror", isTeamcityBuild)

compiler/build.gradle.kts

@@ -86,7 +86,7 @@ if (kotlinBuildProperties.isInJpsBuildIdeaSync) {
     idea {
         this.module.generatedSourceDirs.add(generationRoot)
     }
-} else if (!kotlinBuildProperties.useFir) {
+} else if (!kotlinBuildProperties.useFir && !kotlinBuildProperties.disableWerror) {
     allprojects {
         tasks.withType<KotlinCompile<*>> {
             if (path !in tasksWithWarnings) {

libraries/commonConfiguration.gradle

@@ -37,6 +37,7 @@ ext.configureJvm6Project = { Project project ->
         }
     }
 
+    if (!BuildPropertiesExtKt.getDisableWerror(project.kotlinBuildProperties)) {
         project.tasks.withType(org.jetbrains.kotlin.gradle.dsl.KotlinCompile.class) { task ->
             if (!tasksWithWarnings.contains(task.path)) {
                 task.kotlinOptions {
@@ -45,6 +46,7 @@ ext.configureJvm6Project = { Project project ->
             }
         }
     }
+}
 
 ext.compileJava9Sources = { Project project, String moduleName, Collection<FileCollection> moduleOutputs = [project.sourceSets.main.output] ->
     // module-info.java should be in java9 source set by convention