Tidied up target triple OS detection. NFC

Use Triple::isOS*() helper functions where possible.

llvm-svn: 222622
diff --git a/llvm/lib/Target/ARM/ARMSubtarget.h b/llvm/lib/Target/ARM/ARMSubtarget.h
index 12899f9..7e83705 100644
--- a/llvm/lib/Target/ARM/ARMSubtarget.h
+++ b/llvm/lib/Target/ARM/ARMSubtarget.h
@@ -347,7 +347,7 @@
   bool isTargetIOS() const { return TargetTriple.isiOS(); }
   bool isTargetLinux() const { return TargetTriple.isOSLinux(); }
   bool isTargetNaCl() const { return TargetTriple.isOSNaCl(); }
-  bool isTargetNetBSD() const { return TargetTriple.getOS() == Triple::NetBSD; }
+  bool isTargetNetBSD() const { return TargetTriple.isOSNetBSD(); }
   bool isTargetWindows() const { return TargetTriple.isOSWindows(); }
 
   bool isTargetCOFF() const { return TargetTriple.isOSBinFormatCOFF(); }