[clang] [clang][analyzer] Add ReportInC99AndEarlier option to DeprecatedOrUnsafeBuf… (PR #168704)

[Balázs Benics via cfe-commits]

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+// Test 1: Without C11 and without flag - should NOT warn
+// RUN: %clang_analyze_cc1 %s -verify=c99-noflag -std=gnu99 \
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steakhal wrote:

So we use `gnu99`; couldn't we use the standard `c99` language flavour instead?
I think the gnu variant allows the gnu extensions, which leads to a strictly broader l language flavour than standard C. Is this intentional?

https://github.com/llvm/llvm-project/pull/168704