init: enable 'user root' check at build time

For visibility.

We could make this only for new API levels, but it isn't
currently exposed at build time, and visibility is good
on upgrades.

Bug: 340953047
Test: build, on device passing and failing requirements
Change-Id: I3a0ea47560c65114bc1b8685954d1fb7687cb8df
diff --git a/init/Android.bp b/init/Android.bp
index dd1f9aa..6992da4 100644
--- a/init/Android.bp
+++ b/init/Android.bp
@@ -571,6 +571,11 @@
     ],
     export_include_dirs: ["test_utils/include"], // for tests
     header_libs: ["bionic_libc_platform_headers"],
+    product_variables: {
+        shipping_api_level: {
+            cflags: ["-DBUILD_SHIPPING_API_LEVEL=%s"],
+        },
+    },
 }
 
 // Host Verifier
@@ -625,6 +630,11 @@
             enabled: false,
         },
     },
+    product_variables: {
+        shipping_api_level: {
+            cflags: ["-DBUILD_SHIPPING_API_LEVEL=%s"],
+        },
+    },
 }
 
 cc_binary {