I think you could rename your header file to c and then inside header_lib.nim
add:
{.compile: "header_lib.c".}
[http://nim-lang.org/docs/manual.html#implementation-specific-pragmas-compile-pragma](http://forum.nim-lang.org///nim-lang.org/docs/manual.html#implementation-specific-pragmas-compile-pragma). There are also ways to pass arguments to the compiler from code [http://nim-lang.org/docs/manual.html#implementation-specific-pragmas-passc-pragma](http://forum.nim-lang.org///nim-lang.org/docs/manual.html#implementation-specific-pragmas-passc-pragma)
