Add system_server to readtracefs group

This allows system_server to search/read tracefs entries. It is needed
for attaching cpu timeinstate bpf programs to tracepoints.

Bug: 208892266
Bug: 209513178
Bug: 214061655
Test: libtimeinstate_test
Change-Id: I4139605eb7c5277887092b3d6a3fb26bf4f8f171
Merged-In: I4139605eb7c5277887092b3d6a3fb26bf4f8f171

core/java/com/android/internal/os/ZygoteInit.java

@@ -783,7 +783,7 @@ public class ZygoteInit {
                 "--setuid=1000",
                 "--setgid=1000",
                 "--setgroups=1001,1002,1003,1004,1005,1006,1007,1008,1009,1010,1018,1021,1023,"
-                        + "1024,1032,1065,3001,3002,3003,3006,3007,3009,3010,3011",
+                        + "1024,1032,1065,3001,3002,3003,3006,3007,3009,3010,3011,3012",
                 "--capabilities=" + capabilities + "," + capabilities,
                 "--nice-name=system_server",
                 "--runtime-args",