PassWrapper: adapt for llvm/llvm-project@d3d856ad8469

LLVM 21 moves to making it more explicit what this function call is
doing, but nothing has changed behaviorally, so for now we just adjust
to using the new name of the function.

@rustbot label llvm-main

Author: durin42

compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp

@@ -1365,7 +1365,12 @@ LLVMRustCreateThinLTOData(LLVMRustThinLTOModule *modules, size_t num_modules,
   // Convert the preserved symbols set from string to GUID, this is then needed
   // for internalization.
   for (size_t i = 0; i < num_symbols; i++) {
+#if LLVM_VERSION_GE(21, 0)
+    auto GUID =
+        GlobalValue::getGUIDAssumingExternalLinkage(preserved_symbols[i]);
+#else
     auto GUID = GlobalValue::getGUID(preserved_symbols[i]);
+#endif
     Ret->GUIDPreservedSymbols.insert(GUID);
   }
 
@@ -1685,11 +1690,11 @@ extern "C" void LLVMRustComputeLTOCacheKey(RustStringRef KeyOut,
   // Based on the 'InProcessThinBackend' constructor in LLVM
 #if LLVM_VERSION_GE(21, 0)
   for (auto &Name : Data->Index.cfiFunctionDefs().symbols())
-    CfiFunctionDefs.insert(
-        GlobalValue::getGUID(GlobalValue::dropLLVMManglingEscape(Name)));
+    CfiFunctionDefs.insert(GlobalValue::getGUIDAssumingExternalLinkage(
+        GlobalValue::dropLLVMManglingEscape(Name)));
   for (auto &Name : Data->Index.cfiFunctionDecls().symbols())
-    CfiFunctionDecls.insert(
-        GlobalValue::getGUID(GlobalValue::dropLLVMManglingEscape(Name)));
+    CfiFunctionDecls.insert(GlobalValue::getGUIDAssumingExternalLinkage(
+        GlobalValue::dropLLVMManglingEscape(Name)));
 #else
   for (auto &Name : Data->Index.cfiFunctionDefs())
     CfiFunctionDefs.insert(