[clang] [clang][SME] Account for C++ lambdas in SME builtin diagnostics (PR #124750)

[Sander de Smalen via cfe-commits]

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+// RUN: %clang_cc1  -triple aarch64-none-linux-gnu -target-feature +sve \
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sdesmalen-arm wrote:

Maybe it makes more sense to move the existing `aarch64-incompat-sm-builtin-calls.c` to `aarch64-incompat-sm-builtin-calls.cpp` (there is nothing C-specific to the exisdting file AIUI) and then adding these new tests.

https://github.com/llvm/llvm-project/pull/124750