[clang] [SystemZ][z/OS] Add guard for dl_info and dladdr (PR #75637)

[Abhina Sree via cfe-commits]

https://github.com/abhina-sree created https://github.com/llvm/llvm-project/pull/75637

This patch fixes the following build error on z/OS `error: unknown type name 'Dl_info'` by adding a guard to check if we have dladdr.

>From 6b102c50136b8f49b2d678b06fb8f14f866cca70 Mon Sep 17 00:00:00 2001
From: Abhina Sreeskantharajan <Abhina.Sreeskantharajan at ibm.com>
Date: Fri, 15 Dec 2023 13:13:24 -0500
Subject: [PATCH] check if we have dlfcn.h and dladdr

---
 clang/tools/libclang/CIndexer.cpp | 8 +++++++-
 1 file changed, 7 insertions(+), 1 deletion(-)

diff --git a/clang/tools/libclang/CIndexer.cpp b/clang/tools/libclang/CIndexer.cpp
index 77da2e4fa5ead0..41f8a6f2dac5fb 100644
--- a/clang/tools/libclang/CIndexer.cpp
+++ b/clang/tools/libclang/CIndexer.cpp
@@ -125,13 +125,19 @@ const std::string &CIndexer::getClangResourcesPath() {
 #elif defined(_AIX)
   getClangResourcesPathImplAIX(LibClangPath);
 #else
+  bool pathNotFound = false;
+#if defined(HAVE_DLFCN_H) && defined(HAVE_DLADDR)
   Dl_info info;
   std::string Path;
   // This silly cast below avoids a C++ warning.
   if (dladdr((void *)(uintptr_t)clang_createTranslationUnit, &info) != 0) {
     // We now have the CIndex directory, locate clang relative to it.
     LibClangPath += info.dli_fname;
-  } else if (!(Path = llvm::sys::fs::getMainExecutable(nullptr, nullptr)).empty()) {
+  } else
+    pathNotFound = true;
+#endif
+  if (pathNotFound &&
+      !(Path = llvm::sys::fs::getMainExecutable(nullptr, nullptr)).empty()) {
     // If we can't get the path using dladdr, try to get the main executable
     // path. This may be needed when we're statically linking libclang with
     // musl libc, for example.