[clang] [clang] Accept lambdas in C++03 as an extensions (PR #73376)

[Nikolas Klauser via cfe-commits]

philnik777 wrote:

@shafik See https://discourse.llvm.org/t/rfc-allow-c-11-lambdas-in-c-03-as-an-extension/75262

https://github.com/llvm/llvm-project/pull/73376