Move compatibility files out of prebuilts dir.

The treble compatibility tests check for policy differences between old
and new policy.  To do this correctly, we must not modify the policy which
represents the older policies.  Move the files meant to be changed to a
different location from the ones that are not meant to be touched to avoid
any undesired changes to old policy, e.g. commit:
2bdefd65078d890889672938c6f0d2accdd25bc5

Bug: 36899958
Test: Build-time tests build.
Change-Id: I8fa3947cfae756f37556fb34e1654382e2e48372

Android.mk

@@ -1192,8 +1192,8 @@ $(built_26.0_plat_sepolicy): $(26.0_plat_policy.conf) $(HOST_OUT_EXECUTABLES)/ch
 # targeting the 26.0 SELinux release.  This ensures that our policy will build
 # when used on a device that has non-platform policy targetting the 26.0 release.
 26.0_compat := $(intermediates)/26.0_compat
-26.0_mapping.cil := $(LOCAL_PATH)/prebuilts/api/26.0/26.0.cil
-26.0_mapping.ignore.cil := $(LOCAL_PATH)/prebuilts/api/26.0/26.0.ignore.cil
+26.0_mapping.cil := $(LOCAL_PATH)/private/compat/26.0/26.0.cil
+26.0_mapping.ignore.cil := $(LOCAL_PATH)/private/compat/26.0/26.0.ignore.cil
 26.0_nonplat := $(LOCAL_PATH)/prebuilts/api/26.0/nonplat_sepolicy.cil
 $(26.0_compat): PRIVATE_CIL_FILES := \
 $(built_plat_cil) $(26.0_mapping.cil) $(26.0_nonplat)

tests/treble_sepolicy_tests.py

@@ -223,7 +223,8 @@ def TestNoUnmappedNewTypes():
     if len(violators) > 0:
         ret += "SELinux: The following types were found added to the policy "
         ret += "without an entry into the compatibility mapping file(s) found "
-        ret += "in prebuilts/api/" + compatMapping.apiLevel + "/\n"
+        ret += "in private/compat/" + compatMapping.apiLevel + "/"
+        ret +=  compatMapping.apiLevel + "[.ignore].cil/n"
         ret += " ".join(str(x) for x in sorted(violators)) + "\n"
     return ret