[tlbuild] build failure: duplicated extern "C" definition of getopt() when compiling a C++ program

[Karl Berry]

    extern int getopt ( ) ; 

Evidently your CC is not defining __cplusplus, which would have avoided
the error.  So what macro does it predefine?

But anyway, I suspect that we can just remove the decl entirely.  I'm
doing that now.  We'll see if that causes new brokenness.