Relax permissions on /data/misc/logd

Incidentd needs to access /data/misc/logd to get persisted logs for
debugging purposes. Relax permissions on /data/misc/logd to allow
group (log) to access the dir and read its files. Effectively change
to:
drwxr-x--- logd log /data/misc/logd
-rw-r----- logd log /data/misc/logd/logcat*

Since this dir stores the past output of logcat, anyone that can run
logcat can be granted access to this dir. Access to this dir is further
guarded by SELinux. So it is safe.

Bug: 147924172
Test: Build, flash, reboot. Verify that the files have the right
      permissions.

Change-Id: I4d2aa9d5883d1ef14411b2b3902f0ca7c641dd7e
diff --git a/logcat/logcat.cpp b/logcat/logcat.cpp
index 7b18438..08e3d22 100644
--- a/logcat/logcat.cpp
+++ b/logcat/logcat.cpp
@@ -110,7 +110,7 @@
 #endif
 
 static int openLogFile(const char* pathname, size_t sizeKB) {
-    int fd = open(pathname, O_WRONLY | O_APPEND | O_CREAT | O_CLOEXEC, S_IRUSR | S_IWUSR);
+    int fd = open(pathname, O_WRONLY | O_APPEND | O_CREAT | O_CLOEXEC, S_IRUSR | S_IWUSR | S_IRGRP);
     if (fd < 0) {
         return fd;
     }