[clang] [SFrame][Retry] Add assembler option --gsframe (PR #165806)

[Tarun Prabhu via cfe-commits]

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@@ -7729,6 +7729,11 @@ def massembler_fatal_warnings : Flag<["-"], "massembler-fatal-warnings">,
 def crel : Flag<["--"], "crel">,
   HelpText<"Enable CREL relocation format (ELF only)">,
   MarshallingInfoFlag<CodeGenOpts<"Crel">>;
+// The leading 'g' is misleading. This is an unwind tables option, not
+// a debug option. But uses this name for gnu compatibility.
+def gsframe : Flag<["--"], "gsframe">,
+              HelpText<"Generate .sframe unwind sections (ELF only)">,
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tarunprabhu wrote:

Since this is only on AArch64 and X86, it may be good to mention that here. This has been done for some other options too, such as `print-supported-extensions`. Since AArch64 has not been supported yet, it should probably just be X86. 

https://github.com/llvm/llvm-project/pull/165806