Add gettid() to SELinux policy in prep for GWP-ASan.

GWP-ASan is a sampled allocator framework that is planned for rollout in
Android R. It instruments the bionic allocator, and requires gettid()
during its initialisation.

Ensure that we can call gettid() from configstore.

Bug: 135634846
Test: N/A

Change-Id: I4a92c989ffde9051831e858e805fc20ae993dc01
diff --git a/configstore/1.1/default/seccomp_policy/configstore@1.1-arm64.policy b/configstore/1.1/default/seccomp_policy/configstore@1.1-arm64.policy
index 937fddd..a609620 100644
--- a/configstore/1.1/default/seccomp_policy/configstore@1.1-arm64.policy
+++ b/configstore/1.1/default/seccomp_policy/configstore@1.1-arm64.policy
@@ -45,6 +45,7 @@
 getdents64: 1
 clock_gettime: 1
 getpid: 1
+gettid: 1
 
 # used during process crash by crash_dump to dump process info
 rt_sigprocmask: 1