[clang] [clang][ssaf] Extract shared tool utilities into `clang-ssaf-tool-common` (PR #187439)

[Aviral Goel via cfe-commits]

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+//===- SSAFToolUtils.cpp - Shared utilities for SSAF tools ---------------===//
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aviralg wrote:

Don't know if this is the right place to keep common code.

https://github.com/llvm/llvm-project/pull/187439