Add "native" to config.available_features, to make it easier to disable non-x-compile-safe tests

Patch by Artyom Skrobov!

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@190681 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/test/lit.cfg b/test/lit.cfg
index d23a40c..3b1c2c1 100644
--- a/test/lit.cfg
+++ b/test/lit.cfg
@@ -256,6 +256,10 @@
 if platform.system() not in ['Windows']:
     config.available_features.add('ansi-escape-sequences')
 
+# Native compilation: host arch == target arch
+if config.host_arch in config.target_triple:
+    config.available_features.add("native")
+
 # Case-insensitive file system
 def is_filesystem_case_insensitive():
     handle, path = tempfile.mkstemp(prefix='case-test', dir=config.test_exec_root)