Make rn_xplat_cxx_library and rn_apple_library target iOS 11

Summary:
This forces individual RN libraries to target SDK 11+

Changelog: [iOS] Make rn_xplat_cxx_library and rn_apple_library target iOS 11

Reviewed By: shergin

Differential Revision: D26179411

fbshipit-source-id: 898201943164ff8e53924eee5ca877103bf0f62a

Author: Peter Argany

tools/build_defs/oss/rn_defs.bzl

@@ -163,7 +163,7 @@ def rn_android_prebuilt_aar(*args, **kwargs):
 def rn_apple_library(*args, **kwargs):
     kwargs.setdefault("link_whole", True)
     kwargs.setdefault("enable_exceptions", True)
-    kwargs.setdefault("target_sdk_version", "10.0")
+    kwargs.setdefault("target_sdk_version", "11.0")
 
     # Unsupported kwargs
     _ = kwargs.pop("autoglob", False)