[llvm] [LegacyLTO] Emit the error message that was silently dropped (PR #152172)

[Steven Wu via llvm-commits]

https://github.com/cachemeifyoucan created https://github.com/llvm/llvm-project/pull/152172

Using LLVMContext to emit the error from `TargetRegistry::lookupTarget`
that was silently ignored and not propagated. This allows user to better
identify the kind of error occured.

rdar://157542119


>From 967d631ba813eb0a525701e73dddaad443aaddf3 Mon Sep 17 00:00:00 2001
From: Steven Wu <stevenwu at apple.com>
Date: Tue, 5 Aug 2025 09:30:45 -0700
Subject: [PATCH] =?UTF-8?q?[=F0=9D=98=80=F0=9D=97=BD=F0=9D=97=BF]=20initia?=
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Created using spr 1.3.6
---
 llvm/lib/LTO/LTOModule.cpp | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/llvm/lib/LTO/LTOModule.cpp b/llvm/lib/LTO/LTOModule.cpp
index e0a975806a31d..7dd06118e2a57 100644
--- a/llvm/lib/LTO/LTOModule.cpp
+++ b/llvm/lib/LTO/LTOModule.cpp
@@ -203,8 +203,10 @@ LTOModule::makeLTOModule(MemoryBufferRef Buffer, const TargetOptions &options,
   // find machine architecture for this module
   std::string errMsg;
   const Target *march = TargetRegistry::lookupTarget(Triple, errMsg);
-  if (!march)
+  if (!march) {
+    Context.emitError(errMsg);
     return make_error_code(object::object_error::arch_not_found);
+  }
 
   // construct LTOModule, hand over ownership of module and target
   SubtargetFeatures Features;