[libc++] Do not set the `availability=XXX` feature when not testing against a system...

Otherwise, the `availability=XXX` lit feature is set even when we're
testing trunk and _LIBCPP_DISABLE_AVAILABILITY is defined, which causes
tests that check for availability markup to be enabled and unexpectedly
pass.

diff --git a/libcxx/utils/libcxx/test/config.py b/libcxx/utils/libcxx/test/config.py
index 215faf2..8d6b901 100644 (file)
--- a/libcxx/utils/libcxx/test/config.py
+++ b/libcxx/utils/libcxx/test/config.py
@@ -418,7 +418,7 @@ class Configuration(object):
         # Configure the availability feature. Availability is only enabled
         # with libc++, because other standard libraries do not provide
         # availability markup.
-        if self.use_deployment and self.cxx_stdlib_under_test == 'libc++':
+        if self.use_deployment and self.cxx_stdlib_under_test == 'libc++' and self.use_system_cxx_lib:
             self.config.available_features.add('availability')
             self.add_deployment_feature('availability')