Revert "[libc++] Only add dylib-related features when using the system's libc++"

This reverts r353319, which broke our internal CI.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@353321 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/utils/libcxx/test/config.py b/utils/libcxx/test/config.py
index f086e66..5c7f4c3 100644
--- a/utils/libcxx/test/config.py
+++ b/utils/libcxx/test/config.py
@@ -1145,7 +1145,7 @@
 
         # Throwing bad_optional_access, bad_variant_access and bad_any_cast is
         # supported starting in macosx10.14.
-        if self.get_lit_conf('use_system_cxx_lib') and name == 'macosx' and version in ('10.%s' % v for v in range(7, 14)):
+        if name == 'macosx' and version in ('10.%s' % v for v in range(7, 14)):
             self.config.available_features.add('dylib-has-no-bad_optional_access')
             self.lit_config.note("throwing bad_optional_access is not supported by the deployment target")