[clang] [Clang] skip default argument instantiation for non-defining friend declarations without specialization info to meet [dcl.fct.default] p4 (PR #113777)

[Alan Zhao via cfe-commits]

alanzhao1 wrote:

> Reverted. The issue looks like the instantiation of the default argument was skipped, but without any previous error actually being produced, so it proceeded to CodeGen with invalid AST.

Thanks! Still waiting on CReduce for that repro.

https://github.com/llvm/llvm-project/pull/113777