Add @xla to Jax's platform mappings config

PiperOrigin-RevId: 620155135

Author: kanglant

platform_mappings

@@ -1,11 +1,11 @@
 platforms:
 #  Maps "--platforms=//tools/toolchains/cross_compile/config:darwin_x86_64"
 #  to "--cpu=darwin".
-  //tools/toolchains/cross_compile/config:darwin_x86_64
+  @xla//tools/toolchains/cross_compile/config:darwin_x86_64
     --cpu=darwin
 
 flags:
   # Maps "--cpu=darwin" to
   # "--platforms=//tools/toolchains/cross_compile/config:darwin_x86_64".
   --cpu=darwin
-    //tools/toolchains/cross_compile/config:darwin_x86_64
+    @xla//tools/toolchains/cross_compile/config:darwin_x86_64