Fix typo in FindCoroutines.cmake

Author: andreasbuhr

cmake/FindCoroutines.cmake

@@ -152,7 +152,7 @@ if(find_final)
     check_include_file_cxx("coroutine" _CXX_COROUTINES_HAVE_HEADER)
     if(_CXX_COROUTINES_HAVE_HEADER)
         check_cxx_source_compiles("#include <coroutine> \n typedef std::suspend_never blub; \nint main() {} " _CXX_COROUTINES_FINAL_HEADER_COMPILES)
-        set(_CXX_COROUTINES_HAVE_HEADER ${}_CXX_COROUTINES_FINAL_HEADER_COMPILES})
+        set(_CXX_COROUTINES_HAVE_HEADER ${_CXX_COROUTINES_FINAL_HEADER_COMPILES})
     endif()
 
     if(NOT _CXX_COROUTINES_HAVE_HEADER)