Allow composd to read ART's properties

Only ro.zygote is currently used, though we'll need to a few others of
the same property context.

Bug: 205750213
Test: composd_cmd forced-odrefresh # less SELinux denial
Change-Id: I2efbbc1637142f522a66c47bdd17471c4bde227a
diff --git a/private/composd.te b/private/composd.te
index 30e26f9..e41533b 100644
--- a/private/composd.te
+++ b/private/composd.te
@@ -22,3 +22,6 @@
 # Run odrefresh to refresh ART artifacts, and kill it if we need to
 domain_auto_trans(composd, odrefresh_exec, odrefresh)
 allow composd odrefresh:process sigkill;
+
+# Read ART's properties
+get_prop(composd, dalvik_config_prop)