[LTO] - Get rid of friend 'computeDeadSymbols'. NFC.

computeDeadSymbols accessed isLive() which was not public
before. It does not make much sence to keep isLive() private
because flags are available via flags() public member anyways.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@323415 91177308-0d34-0410-b5e6-96231b3b80d8
1 file changed