[clang] [flang] [mlir] [Flang][Driver] Added support for -funique-internal-linkage-names option (PR #216680)

[Tarun Prabhu via cfe-commits]

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tarunprabhu wrote:

>From what I can tell, this test is very similar to the other test, `function-attr-unique-internal-linkage-names.fir` that also has an almost identical file name. Can we merge the two?

https://github.com/llvm/llvm-project/pull/216680