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.

#ifndef LDC_IR_IRDTYPE_H
#define LDC_IR_IRDTYPE_H

#include <set>

namespace llvm {
    class PATypeHolder;
}

struct IrDType
{
    IrDType();
    llvm::PATypeHolder* type;
};

#endif