[opt] Properly report errors when loading pass plugins (#69745)

All error messages here already contain the path to the plugin, so no
need to repeat it in opt.cpp.

Author: aeubanks

llvm/test/Feature/load_plugin_error.ll

@@ -0,0 +1,5 @@
+; REQUIRES: plugins, examples
+; UNSUPPORTED: target={{.*windows.*}}
+
+; RUN: not opt < %s -load-pass-plugin=%t/nonexistant.so -disable-output 2>&1 | FileCheck %s
+; CHECK: Could not load library {{.*}}nonexistant.so

llvm/tools/opt/opt.cpp

@@ -39,6 +39,7 @@
 #include "llvm/Passes/PassPlugin.h"
 #include "llvm/Remarks/HotnessThresholdParser.h"
 #include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/InitLLVM.h"
 #include "llvm/Support/PluginLoader.h"
@@ -440,11 +441,8 @@ int main(int argc, char **argv) {
   SmallVector<PassPlugin, 1> PluginList;
   PassPlugins.setCallback([&](const std::string &PluginPath) {
     auto Plugin = PassPlugin::Load(PluginPath);
-    if (!Plugin) {
-      errs() << "Failed to load passes from '" << PluginPath
-             << "'. Request ignored.\n";
-      return;
-    }
+    if (!Plugin)
+      report_fatal_error(Plugin.takeError(), /*gen_crash_diag=*/false);
     PluginList.emplace_back(Plugin.get());
   });