bug_map: Update denial metadata to have prefix "bug="

In Android Q and earlier, the format of bug_map file is:
  <scontext> <tcontext> <tclass> <bugid>
and the bugid is prepended with a "b/" prefix implicitly.

In Android R, the format is generalized to encode arbitrary text:
  <scontext> <tcontext> <tclass> <bug_description>
so if the bug_description is a bugid, the bug would need to have a "b/"
prefix explicitly:
  <scontext> <tcontext> <tclass> b/<bugid>

This causes trouble on GSI mixed version testing.
For example, if a S GSI is mixed with Q vendor, then the logd logger (S)
would expect the bug_map file to have explicit "b/" prefix, however the
bug_map, which is from vendor partition, don't have any "b/" prefix,
because it (Q) assumes that the logger would prepend the "b/" prefix for
them.

To remedy this problem, let's unconditionally prepend bug_map metadata
with a "bug=" prefix, so for S+Q configurations the log would look like:
  avc: denied ... bug=178056724
for ordinary S device:
  avc: denied ... bug=b/178056724
  avc: denied ... bug=<arbitrary text>
This would make the format of bug_map metadata more consistent, and
DeviceBootTest#SELinuxUncheckedDenialBootTest would be able to parse
bug_map metadata for both cases.

Bug: 178577550
Test: Trigger some denials, verify that the denials are tagged with
  "bug=<bugid>"
Test: DeviceBootTest#SELinuxUncheckedDenialBootTest passes
Change-Id: Ic28981a15ce4ab635bfdc9596668c2f1326a8aa6
2 files changed
tree: 432b1d29b03491512d704550de0bf7def1ceba20
  1. liblog/
  2. logcat/
  3. logd/
  4. logwrapper/
  5. OWNERS
  6. PREUPLOAD.cfg
  7. TEST_MAPPING