Hack to make compiling the tango 0.99.8 runtime work. The gc has no module statements and the new frontend fails to find the imports. So I add an explicit include path to the runtime gc directory.

#ifndef __LDC_GEN_WARNINGS_H__
#define __LDC_GEN_WARNINGS_H__

void warnInvalidPrintfCall(Loc loc, Expression* arguments, size_t nargs);

#endif // __LDC_GEN_WARNINGS_H__