[llvm-debuginfod-find] Fix help text regression (#110752)

While porting the tool from using cl:opt to OptTable, I had mistakenly
deleted the help text header that was originally part of the tool.
Bringing it back in this patch.

Author: Prabhuk

llvm/tools/llvm-debuginfod-find/llvm-debuginfod-find.cpp

@@ -77,9 +77,15 @@ static void parseArgs(int argc, char **argv) {
       });
 
   if (Args.hasArg(OPT_help)) {
-    Tbl.printHelp(llvm::outs(),
-                  "llvm-debuginfod-find [options] <input build_id>",
-                  ToolName.str().c_str());
+    Tbl.printHelp(
+        llvm::outs(), "llvm-debuginfod-find [options] <input build_id>",
+        "llvm-debuginfod-find: Fetch debuginfod artifacts\n\n"
+        "This program is a frontend to the debuginfod client library. The "
+        "cache directory, request timeout (in seconds), and debuginfod server "
+        "urls are set by these environment variables:\n"
+        "DEBUGINFOD_CACHE_PATH (default set by sys::path::cache_directory)\n"
+        "DEBUGINFOD_TIMEOUT (defaults to 90s)\n"
+        "DEBUGINFOD_URLS=[comma separated URLs] (defaults to empty)");
     std::exit(0);
   }