clang/test/Driver/darwin-sdkroot.c: Suppress this on msys bash, to introduce the feature "shell-preserves-root".

MSYS transforms '/' to 'X:/mingwroot/'.

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@172598 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/Driver/darwin-sdkroot.c b/test/Driver/darwin-sdkroot.c
index f463f4a..b727fa6 100644
--- a/test/Driver/darwin-sdkroot.c
+++ b/test/Driver/darwin-sdkroot.c
@@ -30,3 +30,6 @@
 // CHECK-NONROOT: clang
 // CHECK-NONROOT: "-cc1"
 // CHECK-NONROOT-NOT: "-isysroot"
+//
+// It doesn't make sense on msys bash.
+// REQUIRES: shell-preserves-root