[llvm] [LTO] Fix used before intialised warning (PR #143705)

[Martin Storsjö via llvm-commits]

mstorsjo wrote:

FWIW, building LLVM with GCC (with modern versions) products loads of warnings. It has never been entirely free of warnings, but it used to be half a dozen or so. I haven’t tried to get rid of the ones that have popped up lately, so there’s quite many these days. If you have time, there may be many more that might be similarly low hanging fruit to silence.

https://github.com/llvm/llvm-project/pull/143705