Make the Apple Skylark rule be able to fetch environment data from the
xcode_config rule in addition to ctx.fragments.apple .

Subsequent Bazel versions won't support these methods on ctx.fragments.apple
and thus need to be updated.

Progress towards https://github.com/bazelbuild/bazel/issues/3424 .

RELNOTES: None.
PiperOrigin-RevId: 171021097

tools/build_defs/apple/shared.bzl

diff --git a/tools/build_defs/apple/shared.bzl b/tools/build_defs/apple/shared.bzl
index 4d62db6..1506edc 100644
--- a/tools/build_defs/apple/shared.bzl
+++ b/tools/build_defs/apple/shared.bzl
@@ -74,8 +74,10 @@
   """Returns the environment dictionary necessary to use xcrunwrapper."""
   platform = ctx.fragments.apple.single_arch_platform
 
-  action_env = ctx.fragments.apple.target_apple_env(platform) \
-      + ctx.fragments.apple.apple_host_system_env()
+  environment_supplier = ctx.attr._xcode_config[apple_common.XcodeVersionConfig]
+  if not hasattr(environment_supplier, "apple_host_system_env"):
+    environment_supplier = ctx.fragments.apple
+  action_env = environment_supplier.target_apple_env(platform) + environment_supplier.apple_host_system_env()
 
   return action_env