Express arm64e via an additional constraint rather than a new cpu constraint

PiperOrigin-RevId: 822571984
(cherry picked from commit 1d41e81912acd95a1b0f301b64b6538530a63b1b)

constraints/BUILD

diff --git a/constraints/BUILD b/constraints/BUILD
index c58ac67..c08006d 100644
--- a/constraints/BUILD
+++ b/constraints/BUILD
@@ -48,6 +48,20 @@
     constraint_setting = ":target_vendor",
 )
 
+# A constraint to indicate whether the platform supports Apple's pointer
+# authentication.
+constraint_setting(
+    name = "pointer_authentication_setting",
+    visibility = ["//visibility:private"],
+)
+
+# If a platform has this constraint_value, it supports Apple's pointer
+# authentication.
+constraint_value(
+    name = "pointer_authentication",
+    constraint_setting = ":pointer_authentication_setting",
+)
+
 # Consumed by bazel tests.
 filegroup(
     name = "for_bazel_tests",

lib/apple_support.bzl

diff --git a/lib/apple_support.bzl b/lib/apple_support.bzl
index e430705..7253802 100644
--- a/lib/apple_support.bzl
+++ b/lib/apple_support.bzl
@@ -276,6 +276,9 @@
         "_x86_64_constraint": attr.label(
             default = Label("@platforms//cpu:x86_64"),
         ),
+        "_pointer_authentication_constraint": attr.label(
+            default = Label("@build_bazel_apple_support//constraints:pointer_authentication"),
+        ),
         "_apple_device_constraint": attr.label(
             default = Label("//constraints:device"),
         ),
@@ -477,8 +480,15 @@
     arm64_32_constraint = ctx.attr._arm64_32_constraint[platform_common.ConstraintValueInfo]
     x86_64_constraint = ctx.attr._x86_64_constraint[platform_common.ConstraintValueInfo]
 
+    pointer_authentication_constraint = (
+        ctx.attr._pointer_authentication_constraint[platform_common.ConstraintValueInfo]
+    )
+
     if ctx.target_platform_has_constraint(arm64_constraint):
-        return "arm64"
+        if ctx.target_platform_has_constraint(pointer_authentication_constraint):
+            return "arm64e"
+        else:
+            return "arm64"
     elif ctx.target_platform_has_constraint(arm64e_constraint):
         return "arm64e"
     elif ctx.target_platform_has_constraint(arm64_32_constraint):