[OpenMP][NFC] Use temporary instead of local to take advantage of move semantics (#138582)

Static analysis flagged `MapnamesName` because we could move it into
`createOffloadMapnames`. I just replaced the local with a direct call to
`createPlatformSpecificName` at the function argument location.

Author: shafik

llvm/lib/Frontend/OpenMP/OMPIRBuilder.cpp

@@ -8378,9 +8378,8 @@ Error OpenMPIRBuilder::emitOffloadingArrays(
 
   // The information types are only built if provided.
   if (!CombinedInfo.Names.empty()) {
-    std::string MapnamesName = createPlatformSpecificName({"offload_mapnames"});
-    auto *MapNamesArrayGbl =
-        createOffloadMapnames(CombinedInfo.Names, MapnamesName);
+    auto *MapNamesArrayGbl = createOffloadMapnames(
+        CombinedInfo.Names, createPlatformSpecificName({"offload_mapnames"}));
     Info.RTArgs.MapNamesArray = MapNamesArrayGbl;
     Info.EmitDebug = true;
   } else {