Fix builds for "download_stripped" targets

We were seeing this:

    bazel run -c opt --config=roborio //y2020:download_stripped -- 971
    ERROR: Target //y2020:download_stripped is incompatible and cannot be built, but was explicitly requested.
    Dependency chain:
        //y2020:download_stripped
        //aos:prime_start_binaries_stripped
        //aos/events/logging:logger_main
        //aos/events/logging:logger
        //aos/events/logging:logfile_utils
        //aos/events/logging:lzma_encoder
        //third_party:lzma
        //third_party:unavailable   <-- target platform didn't satisfy constraint @platforms//:incompatible
    INFO: Elapsed time: 31.343s
    INFO: 0 processes.
    FAILED: Build did NOT complete successfully (127 packages loaded, 31974 targets configured)
    FAILED: Build did NOT complete successfully (127 packages loaded, 31974 targets configured)

I accidentally removed some logic I shouldn't have. This patch should
make the invocation work again.

Change-Id: Ia77e403baedcb1d130936ed3c5b51903ed8389c4
diff --git a/debian/python.BUILD b/debian/python.BUILD
index 7abcf1f..c840a19 100644
--- a/debian/python.BUILD
+++ b/debian/python.BUILD
@@ -10,6 +10,7 @@
         "usr/include/",
         "usr/include/python3.5m/",
     ],
+    target_compatible_with = ["@platforms//cpu:x86_64"],
     visibility = ["//visibility:public"],
 )
 
@@ -47,6 +48,7 @@
         "usr/include/",
         "usr/include/python2.7/",
     ],
+    target_compatible_with = ["@platforms//cpu:x86_64"],
     visibility = ["//visibility:public"],
 )