External .o sources + BetterC : undefined symbol: __chkstk

[SrMordred via Digitalmars-d-learn]

I got undefined symbol: __chkstk when using some external .o 
sources ( compile with clang ) + betterC flag.

I thought that __chkstk was present on ntdll.lib, so i added 
manually as a lib, but still didn´t work.

How can i solve this? (it must be another lib that D includes 
since it works without the betterC flag.)