[K/N][build] Composite build with build.tools-conventions plugin

Adds convention plugin instead of sources inclusion
inside the buildSrc, effectively reducing the amount
of the code to be compiled in buildSrc.

Merge-request: KT-MR-8898

kotlin-native/common/build.gradle.kts

@@ -4,6 +4,7 @@
  */
 
 plugins {
+    id("kotlin.native.build-tools-conventions")
     id("compile-to-bitcode")
 }