[lld] [lld-macho] Fix bug in makeSyntheticInputSection when -dead_strip flag is specified (PR #86878)

[Kyungwoo Lee via llvm-commits]

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@@ -377,7 +377,7 @@ static void handleSectionBoundarySymbol(const Undefined &sym, StringRef segSect,
     // live. Marking the isec live ensures an OutputSection is created that the
     // start/end symbol can refer to.
     assert(sym.isLive());
-    isec->live = true;
+    assert(isec->live == true);
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kyulee-com wrote:

Nit: you could do `assert(isec->live);`

https://github.com/llvm/llvm-project/pull/86878