Currently, zygote spawned apps are prohibited from modifying GPS
data files. If someone tries to allow GPS access to any app domain,
it generates a compile time / CTS exception.

Relax the rules slightly for system_app. These apps run with UID=system,
and shouldn't be banned from handling gps data files.

This change doesn't add or remove any SELinux rules. Rather, it just
relaxes a compile time assertion, allow partners to create SELinux
rules allowing the access if they desire.

(cherrypick from commit 480374e4)

Bug: 18021422
Change-Id: Iad0c6a3627efe129246e2c817f6f71d2735eba93