Suppress signed/unsigned comparison warning.

Author: zygoloid

toolchain/check/cpp/location.cpp

@@ -34,7 +34,7 @@ static auto GetFileInfo(Context& context, SemIR::CheckIRId ir_id) -> FileInfo {
 
   // If we've seen this file before, reuse the same FileID.
   auto& file_start_locs = context.cpp_carbon_file_locations();
-  if (file_start_locs.size() <= file_index) {
+  if (static_cast<int>(file_start_locs.size()) <= file_index) {
     // Never valid; prepare a slot for the caching below.
     file_start_locs.resize(file_index + 1);
   } else if (file_start_locs[file_index].isValid()) {