Prepare new plat-tools SDK component with 2 llvm versions.

Prepare new plat-tools SDK component with 2 llvm versions.

The output of the platform tree build is llvm-rs-cc-2 and should
be used for apps targeting 12+. This is encoded in llvm-rs-cc.txt

The older (HC) version of llvm-rs-cc is copied from the prebuilt
and is used for apps targeting 11+.

Until new tools that can read/process llvm-rs-cc.txt are released,
old tools will use the HC version of llvm-rs-cc which ensure
proper compatibility.

Change-Id: Iddb924409cc9238531bf1a0448b14b7eac3396a5