[clang] [clang] Ensure `--print-runtime-dir` path exists (PR #102834)

[Alexandre Ganea via cfe-commits]

https://github.com/aganea created https://github.com/llvm/llvm-project/pull/102834

Before this PR, `clang --print-runtime-dir` used to report a non-existant directory if `LLVM_ENABLE_PER_TARGET_RUNTIME_DIR=OFF`.

We now check if any of the known runtime directories exist before printing on stdout. If it doesn't, we print `(runtime dir is not present)`.

>From d1d1340b6876d83d48949306e43c723696bf4753 Mon Sep 17 00:00:00 2001
From: Alexandre Ganea <aganea at havenstudios.com>
Date: Sun, 11 Aug 2024 19:03:14 -0400
Subject: [PATCH] [clang] Ensure --print-runtime-dir exits

Before this PR, `clang --print-runtime-dir` used to report a non-existant
directory if LLVM_ENABLE_PER_TARGET_RUNTIME_DIR=OFF.

We now check if any of the known runtime directories exist before
printing on stdout.
---
 clang/lib/Driver/Driver.cpp | 12 ++++++++----
 1 file changed, 8 insertions(+), 4 deletions(-)

diff --git a/clang/lib/Driver/Driver.cpp b/clang/lib/Driver/Driver.cpp
index f4e909b79389bc..4c8cd36dd118ee 100644
--- a/clang/lib/Driver/Driver.cpp
+++ b/clang/lib/Driver/Driver.cpp
@@ -2230,10 +2230,14 @@ bool Driver::HandleImmediateArgs(Compilation &C) {
   }
 
   if (C.getArgs().hasArg(options::OPT_print_runtime_dir)) {
-    if (std::optional<std::string> RuntimePath = TC.getRuntimePath())
-      llvm::outs() << *RuntimePath << '\n';
-    else
-      llvm::outs() << TC.getCompilerRTPath() << '\n';
+    for (auto RuntimePath :
+         {TC.getRuntimePath(), std::make_optional(TC.getCompilerRTPath())}) {
+      if (RuntimePath && getVFS().exists(*RuntimePath)) {
+        llvm::outs() << *RuntimePath << '\n';
+        return false;
+      }
+    }
+    llvm::outs() << "(runtime dir is not present)" << '\n';
     return false;
   }