[clang] [clang-sycl-linker] Fix use of uninitialized memory in temp files (PR #114488)

[Nick Sarnie via cfe-commits]

sarnex wrote:

PR title fixed, thanks.

@jhuber6 @bader This should be ready for merge. CI fails are not related and the failing test is passing in the sanitizer tests now. Thx.

https://github.com/llvm/llvm-project/pull/114488