r203624 - Be case sensitive when determining driver mode based on argv[0] except on Windows

[Anton Korobeynikov]

> I suggested _WIN32, because that is also used further down in the file (around line 448).  But if LLVM_ON_WIN32 is more correct, it should probably be used everywhere?
It's the common idiom used at least in llvm's Support library
(LLVM_ON_UNIX / LLVM_ON_WIN32).

-- 
With best regards, Anton Korobeynikov
Faculty of Mathematics and Mechanics, Saint Petersburg State University