llvm-wrapper: adapt for LLVM 20 API changes

No functional changes intended.

Adapts llvm-wrapper for the LLVM commit
llvm/llvm-project@0f22d47.

Author: krasimirgg

compiler/rustc_llvm/llvm-wrapper/PassWrapper.cpp

@@ -1618,9 +1618,15 @@ extern "C" void LLVMRustComputeLTOCacheKey(RustStringRef KeyOut,
     CfiFunctionDecls.insert(
         GlobalValue::getGUID(GlobalValue::dropLLVMManglingEscape(Name)));
 
+#if LLVM_VERSION_GE(20, 0)
+  Key = llvm::computeLTOCacheKey(conf, Data->Index, ModId, ImportList,
+                                 ExportList, ResolvedODR, DefinedGlobals,
+                                 CfiFunctionDefs, CfiFunctionDecls);
+#else
   llvm::computeLTOCacheKey(Key, conf, Data->Index, ModId, ImportList,
                            ExportList, ResolvedODR, DefinedGlobals,
                            CfiFunctionDefs, CfiFunctionDecls);
+#endif
 
   LLVMRustStringWriteImpl(KeyOut, Key.c_str(), Key.size());
 }