Allow priv_app system_linker_exec:file execute_no_trans

Chrome Crashpad uses the the dynamic linker to load native executables
from an APK (b/112050209, crbug.com/928422)

We made the equivalent change to untrusted_app_all in
9ea8c0701d162ec40d30b079778723d908e0edca but webview also runs in
priv_app contexts.

(Cherry-pick of 25cb9046efb2d1b8b3322f3e11ef7915010befad, with manual
update to the prebuilts.)

Bug: http://b/112050209
Test: treehugger
Change-Id: I19bbadc7f9c9e668e2c6d932c7da24f18e7731bd
4 files changed