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 nested9;
extern(C) int printf(char*, ...);

void main()
{
    int i = 42;
    int func()
    {
        return i + 1;
    }
    int j = func();
    printf("j = %d\n", j);
    assert(j == 43);
}