runsc: support symlink to the exec path.
runsc: support symlink to the exec path.

PiperOrigin-RevId: 201049912
Change-Id: Idd937492217a4c2ca3d59c602e41576a3b203dd9

google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor,google/gvisor