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 bug1;
struct Foo { Foo opSub(ref Foo b) { return Foo(); } }
struct Bar { Foo whee; }
void test(ref Bar moo) { Foo nngh; auto plonk = nngh - moo.whee; }
void main() { Bar bar; test(bar); }