[libc++] Split features for platform detection into its own function

This will allow refactoring how the locales are figured out more easily.

libcxx/utils/libcxx/test/config.py

@@ -355,8 +355,6 @@ def configure_features(self):
                 self.config.available_features.add(f.strip())
         self.target_info.add_locale_features(self.config.available_features)
 
-        target_platform = self.target_info.platform()
-
         # Write an "available feature" that combines the triple when
         # use_system_cxx_lib is enabled. This is so that we can easily write
         # XFAIL markers for tests that are known to fail with versions of
@@ -379,8 +377,8 @@ def configure_features(self):
             self.config.available_features.add('availability=%s' % name)
             self.config.available_features.add('availability=%s%s' % (name, version))
 
-        # Insert the platform name into the available features as a lower case.
-        self.config.available_features.add(target_platform)
+        # Insert the platform name and version into the available features.
+        self.target_info.add_platform_features(self.config.available_features)
 
         # Simulator testing can take a really long time for some of these tests
         # so add a feature check so we can REQUIRES: long_tests in them

libcxx/utils/libcxx/test/target_info.py

@@ -40,6 +40,9 @@ def configure_env(self, env): pass
     def allow_cxxabi_link(self): return True
     def use_lit_shell_default(self): return False
 
+    def add_platform_features(self, features):
+        features.add(self.platform())
+
     def add_path(self, dest_env, new_path):
         if not new_path:
             return
@@ -229,6 +232,10 @@ def platform_ver(self):
 
     def add_locale_features(self, features):
         self.add_common_locales(features)
+
+    def add_platform_features(self, features):
+        super(LinuxLocalTI, self).add_platform_features(features)
+
         # Some linux distributions have different locale data than others.
         # Insert the distributions name and name-version into the available
         # features to allow tests to XFAIL on them.