[libc++] Populate a lit feature including the compiler patch level

If the compiler is (for example) AppleClang 10.0.1, we would previously
populate the following lit features:


This patch additionally populates a feature called 'apple-clang-10.0.1',
which allows more precise enabling/disabling of tests.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@369406 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/libcxx/test/config.py b/utils/libcxx/test/config.py
index e074df3..641bd4a 100644
--- a/utils/libcxx/test/config.py
+++ b/utils/libcxx/test/config.py
@@ -233,11 +233,13 @@
         cxx_type = self.cxx.type
         if cxx_type is not None:
             assert self.cxx.version is not None
-            maj_v, min_v, _ = self.cxx.version
+            maj_v, min_v, patch_v = self.cxx.version
             self.config.available_features.add('%s-%s' % (cxx_type, maj_v))
             self.config.available_features.add('%s-%s.%s' % (
                 cxx_type, maj_v, min_v))
+            self.config.available_features.add('%s-%s.%s.%s' % (
+                cxx_type, maj_v, min_v, patch_v))
         self.cxx.compile_env = dict(os.environ)
         # 'CCACHE_CPP2' prevents ccache from stripping comments while
         # preprocessing. This is required to prevent stripping of '-verify'