Build: implement useBootstrapStdlib flag

Excludes stdlib projects from build and uses bootstrap stdlib artifacts

 #KT-29205

prepare/compiler-embeddable/build.gradle.kts

@@ -6,7 +6,7 @@ plugins {
 }
 
 dependencies {
-    runtime(project(":kotlin-stdlib"))
+    runtime(kotlinStdlib())
     runtime(project(":kotlin-script-runtime"))
     runtime(project(":kotlin-reflect"))
     runtime(commonDep("org.jetbrains.intellij.deps", "trove4j"))