Add host_supported to libhardware_headers.

This will allow building PureSoftKeymaster on the host.

Bug: 155328339
Test: Compiles
Change-Id: If4474fc3da715a49f2c8649a61968cdda9b1086f
diff --git a/Android.bp b/Android.bp
index 72c924f..15f2742 100644
--- a/Android.bp
+++ b/Android.bp
@@ -27,6 +27,7 @@
         },
     },
     min_sdk_version: "29",
+    host_supported: true,
 
 }