[lld] [LLD] [COFF] Add a separate option for allowing duplicate weak symbols (PR #68077)

[Fangrui Song via llvm-commits]

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@@ -1,4 +1,9 @@
 RUN: lld-link -lldmingw %S/Inputs/gnu-weak.o %S/Inputs/gnu-weak2.o -out:%t.exe
+RUN: lld-link -lld-allow-duplicate-weak %S/Inputs/gnu-weak.o %S/Inputs/gnu-weak2.o -out:%t.exe
+RUN: not lld-link %S/Inputs/gnu-weak.o %S/Inputs/gnu-weak2.o -out:%t.exe 2>&1 | FileCheck %s --check-prefix=DEFAULT-ERROR
+
+DEFAULT-ERROR: error: duplicate symbol: weakfunc
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MaskRay wrote:

If this is the last line, consider adding `DEFAULT-ERROR-NOT: {{.}}` as a change detector when the diagnostic improves.

https://github.com/llvm/llvm-project/pull/68077