[lld] [ELF] Move elf::symtab into Ctx (PR #109612)

[Peter Smith via llvm-commits]

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@@ -1265,7 +1265,7 @@ void elf::processArmCmseSymbols() {
     return;
   // Only symbols with external linkage end up in symtab, so no need to do
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smithp35 wrote:

Could replace symtab with ctx.symtab in the comment.

https://github.com/llvm/llvm-project/pull/109612