Automatically detect and use clang verify in failure tests.

Automatically enable clang verify whenever the '-verify-ignore-unexpected' flag
is supported.
Failure tests are run using verify if they contain one or more "expected-*"
diagnostics tags. Otherwise they are run normally.


git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@241492 91177308-0d34-0410-b5e6-96231b3b80d8

test/libcxx/compiler.py

@@ -139,7 +139,10 @@ class CXXCompiler(object):
         return lit.util.capture(cmd).strip()
 
     def hasCompileFlag(self, flag):
-        flags = [flag]
+        if isinstance(flag, list):
+            flags = list(flag)
+        else:
+            flags = [flag]
         # Add -Werror to ensure that an unrecognized flag causes a non-zero
         # exit code. -Werror is supported on all known compiler types.
         if self.type is not None: