emulator: Add option to control SELinux enforcement.

This change adds the following command line
options to the emulator:

  -selinux disabled
  -selinux permissive

This configures SELinux in either permissive or disabled modes.

"disabled" completely disables userspace support for SELinux. No
policy is ever loaded, nor is the SELinux filesystem /sys/fs/selinux
ever mounted.

"permissive" loads the SELinux policy, but puts SELinux into
permissive mode. SELinux policy violations are logged, but not rejected.

Change-Id: I97974deb5b39d5caab36032e8b282281c1e478ea
diff --git a/android/cmdline-options.h b/android/cmdline-options.h
index 16edeac..0c75783 100644
--- a/android/cmdline-options.h
+++ b/android/cmdline-options.h
@@ -166,6 +166,8 @@
 
 OPT_FLAG( force_32bit, "always use 32-bit emulator" )
 
+OPT_PARAM(selinux, "<disabled|permissive>", "Set SELinux to either disabled or permissive mode")
+
 #undef CFG_FLAG
 #undef CFG_PARAM
 #undef OPT_FLAG