Mark llvm headers and libLLVMSupport as vendor_available

They are depended by libbcinfo which is a VNDK-SP library.
Since they are headers and static library, vendor_available: true is
enough.

Bug: 64425518
Test: BOARD_VNDK_VERSION=current m -j libbcinfo.vendor

Change-Id: I4415abb6779776758e780a008c560cbb4ef2c020
7 files changed