Add build properties for attestation feature

The properties for attestation are congifured in build.prop files and
used by frameworks Build.java.
Allow vendor_init to set these properties and allow Zygote to access
them.

Bug: 211547922
Test: SELinuxUncheckedDenialBootTest
Change-Id: I5666524a9708c6fefe113ad4109b8a344405ad57
diff --git a/private/incidentd.te b/private/incidentd.te
index c1314a8..e86b3bf 100644
--- a/private/incidentd.te
+++ b/private/incidentd.te
@@ -193,6 +193,9 @@
   get_prop(incidentd, last_boot_reason_prop);
 ')
 
+# Allow incident to read the build properties for attestation feature
+get_prop(incidentd, build_attestation_prop);
+
 ###
 ### neverallow rules
 ###