Mark libraries required by libbcinfo as vendor_available

libLLVMBitWriter_3_2 and libStripUnkAttr are used by libbcinfo, which is
a vndk-sp library. Mark them as vendor_available:true so that they are
available when building libbcinfo.so

Bug: 64425518
Bug: 64395154
Test: BOARD_VNDK_VERSION=current m -j libbcinfo.so
Merged-In: I7a59aabcae0207d9d4a19df11c89d0008ddbb039
Change-Id: I7a59aabcae0207d9d4a19df11c89d0008ddbb039
(cherry picked from commit 472a71534ac82a590c3ca8b390a9298c7f32057d)
2 files changed