Open /data/anr/traces.txt with O_APPEND.

Should fix selinux denial:
    audit(0.0:7893): avc: denied { write } for path="/data/anr/traces.txt" dev="sda35" ino=679938 scontext=u:r:crash_dump:s0 tcontext=u:object_r:anr_data_file:s0 tclass=file permissive=0

Bug: 35727090
Test: none
Change-Id: I5c131ca1ee48ed00934a9aa7c611ee35fc4f9f2a
1 file changed