[llvm] [llvm-readobj,ELF] Support --decompress/-z (PR #82594)

[Fangrui Song via llvm-commits]

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@@ -0,0 +1,67 @@
+# REQUIRES: zlib
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MaskRay wrote:

I think Windows is a popular OS that often misses zlib support. However, "often" may degrade to "sometimes". Anyway, I just added `decompress-zstd-unsupported.test`...

https://github.com/llvm/llvm-project/pull/82594