[GWP-ASan] Add sysprop, allow shell and system apps to set it.

Bug: 219651032
Test: atest bionic-unit-tests

Change-Id: Ic4804ce0e4f3b6ba8eb8d82aca11b400b45c03dc
diff --git a/private/shell.te b/private/shell.te
index ae5ff55..2ddd7bc 100644
--- a/private/shell.te
+++ b/private/shell.te
@@ -230,3 +230,6 @@
 
 # Allow shell to set persist.wm.debug properties
 userdebug_or_eng(`set_prop(shell, persist_wm_debug_prop)')
+
+# Allow shell to write GWP-ASan properties even on user builds.
+set_prop(shell, gwp_asan_prop)