--- src/runtime/CMakeLists.txt.orig	2024-05-28 01:51:11 UTC
+++ src/runtime/CMakeLists.txt
@@ -150,6 +150,7 @@ set(RUNTIME_CXX_FLAGS
 # Note: ensure that these flags match the flags in the Makefile.
 # Note: this always uses Clang-from-LLVM for compilation, so none of these flags should need conditionalization.
 set(RUNTIME_CXX_FLAGS
+    -Dfopen64=fopen
     -O3
     -std=c++17
     -ffreestanding
