Factor out the code to find gcc, and add a command-line option to override the default executable name. This should help cross-compilation by allowing a cross-gcc to be specified from the configuration file instead of only through the CC environment variable.

module virtcall;

extern(C) int printf(char*, ...);

class C
{
    override char[] toString()
    {
        return "overridden";
    }
}

void main()
{
    C c = new C;
    auto s = c.toString();
    printf("%.*s\n", s.length, s.ptr);
}