Dup file descriptor to prevent double close in oat writer.

Bug: 36404686
Test: art --profile --verbose -Xcompiler-option
--compiler-filter=speed-profile -cp benchmarks.dex
benchmarks.CaffeineLoop.java.CaffeineLoop

Change-Id: I4f43627a331b51a3f3a878a75694664c31a0c8b0