Enable odrefresh to work with composd.

composd spawns odrefresh in its usual domain. odrefresh then spawns
fd_server in a different domain, and makes binder calls back to
composd to perform individual compilation steps.

fd_server is fairly generic, and part of the virt APEX, but this
instance is specific to composd (e.g. it has access to ART files), so
I named the domain composd_fd_server.

Bug: 186126194
Test: Run composd_cmd, artifacts generated
Change-Id: I5a431dd00b5b396a67021c618fc6edcfb25aa21b
diff --git a/private/file.te b/private/file.te
index 124309c..7e0bdd2 100644
--- a/private/file.te
+++ b/private/file.te
@@ -68,3 +68,6 @@
 
 # /dev/kvm
 type kvm_device, dev_type;
+
+# /apex/com.android.virt/bin/fd_server
+type fd_server_exec, system_file_type, exec_type, file_type;