[lld] [LLD] [Build Issue] Ubuntu24 build failure due to LLD's COFF regression (PR #98447)

[Reid Kleckner via llvm-commits]

rnk wrote:

I think there's a real bug here.

It seems extremely sketchy that we don't initialize `isUsedInRegularObj` in the Symbol constructor, but that must be intentional. I'm pretty sure the compiler is entitled to zero initialize the whole object during the constructor, and that may be what @vg0204 is observing with some new GCC version on Ubuntu 24. And, with that toolchain, the bug is reliably observable in the regression test suite.

If we zero initialize the member in all builds, does that cause tests to fail, and then does this patch fix it? I think that's the next thing to try here.

https://github.com/llvm/llvm-project/pull/98447