system_server: (eng builds) remove JIT capabilities

23cde877 removed JIT capabilities
from system_server for user and userdebug builds. Remove the capability
from eng builds to be consistent across build types.

Add a neverallow rule (compile time assertion + CTS test) to verify
this doesn't regress on our devices or partner devices.

Bug: 23468805
Bug: 24915206
Change-Id: Ib2154255c611b8812aa1092631a89bc59a27514b

system_server.te

@@ -7,13 +7,6 @@ type system_server, domain, mlstrustedsubject;
 # Define a type for tmpfs-backed ashmem regions.
 tmpfs_domain(system_server)
 
-eng(`
-  # JIT mappings
-  allow system_server self:process execmem;
-  allow system_server ashmem_device:chr_file execute;
-  allow system_server system_server_tmpfs:file execute;
-')
-
 # For art.
 allow system_server dalvikcache_data_file:file execute;
 allow system_server dalvikcache_data_file:dir r_dir_perms;
@@ -472,3 +465,8 @@ neverallow system_server {
 # the frp_block_device. This helps avoid a system_server to root
 # escalation by writing to raw block devices.
 neverallow system_server { dev_type -frp_block_device }:blk_file no_rw_file_perms;
+
+# system_server should never use JIT functionality
+neverallow system_server self:process execmem;
+neverallow system_server ashmem_device:chr_file execute;
+neverallow system_server system_server_tmpfs:file execute;