trace_processor: add host_supported label to trace_processor_shell

When we enabled building shell on Android, we accidentally broken
building it on the host. Readd support for this.

Bug: 139542649
Change-Id: Ie0a958fc67a24dee75425d7e98b4787d0aeb72e0
diff --git a/Android.bp b/Android.bp
index 7baecb2..0bafd57 100644
--- a/Android.bp
+++ b/Android.bp
@@ -4819,6 +4819,7 @@
     "libprotobuf-cpp-full",
     "libz",
   ],
+  host_supported: true,
   generated_headers: [
     "gen_merged_sql_metrics",
     "perfetto_protos_perfetto_common_zero_gen_headers",