[lld] [lld-macho] Fix unchecked Error crash for thin archive missing child (PR #97169)

[Daniel Bertalan via llvm-commits]

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+# REQUIRES: x86
+
+## We only save those archive members from thin archives in the repro file that are actually used
+## during linking. This means that if we just iterate members, some of them might not exist.
+## Test that that we handle missing members correctly and don't assert on an unchecked Error.
+# FIXME: Should we eagerly save all members instead?
+
+# RUN: rm -rf %t; mkdir %t
+# RUN: sed s/SYM/_main/   %s | llvm-mc -filetype=obj -triple=x86_64-apple-macos -o %t/main.o
+# RUN: sed s/SYM/_unused/ %s | llvm-mc -filetype=obj -triple=x86_64-apple-macos -o %t/unused.o
+
+# RUN: cd %t; llvm-ar rcsT unused.a unused.o
+## FIXME: Absolute paths don't end up relativized in the repro file.
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BertalanD wrote:

This is #97845

https://github.com/llvm/llvm-project/pull/97169