[clang] [llvm] [RISCV] Avoid fatal error for SiFive CLIC preemptible frame pointers (PR #217949)

[Sam Elliott via cfe-commits]

================
@@ -26319,8 +26239,9 @@ SDValue RISCVTargetLowering::LowerFormalArguments(
       reportFatalUsageError("'rnmi' interrupt kind requires Srnmi extension");
     const TargetFrameLowering *TFI = Subtarget.getFrameLowering();
     if (Kind.starts_with("SiFive-CLIC-preemptible") && TFI->hasFP(MF))
-      reportFatalUsageError("'SiFive-CLIC-preemptible' interrupt kinds cannot "
-                            "have a frame pointer");
+      Func.getContext().diagnose(DiagnosticInfoUnsupported{
+          Func, "'SiFive-CLIC-preemptible' interrupt kinds cannot have a frame "
+                "pointer; consider compiling with '-fomit-frame-pointer'"});
----------------
lenary wrote:

```suggestion
          Func, "'SiFive-CLIC-preemptible' interrupt functions cannot have a frame "
                "pointer"});
```

https://github.com/llvm/llvm-project/pull/217949