Move strip-kotlin-annotations script to buildSrc

... and invoke it directly in kotlin-reflect's build file, instead of
running another instance of compiler to evaluate a script. Also only
strip kotlin.Metadata, since it's the only annotation with heavy
metadata on Kotlin-generated class files

build.gradle.kts

@@ -64,8 +64,6 @@ allprojects {
 extra["kotlin_root"] = rootDir
 
 val bootstrapCompileCfg = configurations.create("bootstrapCompile")
-val scriptCompileCfg = configurations.create("scriptCompile").extendsFrom(bootstrapCompileCfg)
-val scriptRuntimeCfg = configurations.create("scriptRuntime").extendsFrom(scriptCompileCfg)
 
 repositories {
     for (repo in (rootProject.extra["repos"] as List<String>)) {