clang/lib/Driver/Driver.cpp: Split COMPILER_PATH according to llvm::sys::PathSeparator, that is ';' in Win32 hosts.

Thanks to Bogon Kim!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@169964 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Driver.cpp b/lib/Driver/Driver.cpp
index 9039600..d41bce5 100644
--- a/lib/Driver/Driver.cpp
+++ b/lib/Driver/Driver.cpp
@@ -238,7 +238,8 @@
   if (char *env = ::getenv("COMPILER_PATH")) {
     StringRef CompilerPath = env;
     while (!CompilerPath.empty()) {
-      std::pair<StringRef, StringRef> Split = CompilerPath.split(':');
+      std::pair<StringRef, StringRef> Split
+        = CompilerPath.split(llvm::sys::PathSeparator);
       PrefixDirs.push_back(Split.first);
       CompilerPath = Split.second;
     }