use DEFAULT_SYSROOT

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@154792 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/Driver/Compilation.cpp b/lib/Driver/Compilation.cpp
index 42c8449..5553fc9 100644
--- a/lib/Driver/Compilation.cpp
+++ b/lib/Driver/Compilation.cpp
@@ -230,3 +230,7 @@
   Redirects[1] = new const llvm::sys::Path();
   Redirects[2] = new const llvm::sys::Path();
 }
+
+StringRef Compilation::getSysRoot(void) const {
+  return getDriver().SysRoot;
+}