Make proc-macro-error-attr available to product and vendor

Bug: 270690570

Test: mma in external/rust/crates
Change-Id: Id03bed68ffa7cf9614156dd2a956c636118a9142
diff --git a/Android.bp b/Android.bp
index 010a3be..208932d 100644
--- a/Android.bp
+++ b/Android.bp
@@ -51,4 +51,6 @@
         "libquote",
     ],
     compile_multilib: "first",
+    product_available: true,
+    vendor_available: true,
 }