[KeyInstr][Clang][NFC] Don't set -dwarf-use-key-instructions

Once #144104 lands the flag is true by default (because each DISubprogram will
track whether or not it's using key instructions).

Author: OCHyams

clang/lib/Driver/ToolChains/Clang.cpp

@@ -4631,11 +4631,8 @@ renderDebugOptions(const ToolChain &TC, const Driver &D, const llvm::Triple &T,
   }
 
   if (Args.hasFlag(options::OPT_gkey_instructions,
-                   options::OPT_gno_key_instructions, false)) {
+                   options::OPT_gno_key_instructions, false))
     CmdArgs.push_back("-gkey-instructions");
-    CmdArgs.push_back("-mllvm");
-    CmdArgs.push_back("-dwarf-use-key-instructions");
-  }
 
   if (EmitCodeView) {
     CmdArgs.push_back("-gcodeview");

clang/test/DebugInfo/KeyInstructions/flag.cpp

@@ -8,8 +8,14 @@
 // HELP-NOT: key-instructions
 
 // KEY-INSTRUCTIONS: "-gkey-instructions"
-// KEY-INSTRUCTIONS: "-mllvm" "-dwarf-use-key-instructions"
 
 // NO-KEY-INSTRUCTIONS-NOT: key-instructions
 
-//// TODO: Add smoke test once some functionality has been added.
+// RUN %clang %s | FileCheck %s --check-prefix=SMOKETEST-OFF
+void f() {}
+// SMOKETEST-OFF-NOT: keyInstructions
+// SMOKETEST-OFF-NOT: atomGroup
+
+// RUN %clang %s -gkey-instructions | FileCheck %s --check-prefix=SMOKETEST-ON
+// SMOKETEST-ON: keyInstructions: true
+// SMOKETEST-ON: atomGroup: 1