Fix error in cmake script

Author: cschreib

tests/CMakeLists.txt

@@ -1,5 +1,5 @@
 function(add_platform_definitions TARGET)
- target_compile_features(oup INTERFACE cxx_std_20)
+ target_compile_features(${TARGET} INTERFACE cxx_std_20)
  if(CMAKE_SYSTEM_NAME MATCHES "Emscripten")
  target_compile_definitions(${TARGET} PRIVATE OUP_PLATFORM_WASM)
  target_compile_definitions(${TARGET} PRIVATE OUP_COMPILER_EMSCRIPTEN)