For DeathTests, we are testing the output of stderr to check if it is the
death we are expecting. To collect the output, Gtest redirects stderr to
a temporary file. But in __libc_write_stderr in libc_logging.cpp, we are
writing to stderr without a O_APPEND flag, so a new message will overwrite
a previous message.
The above situation makes almost all the DeathTests fail on host. Because
the expected message are always overwritten in host DeathTests. So I add
O_APPEND flag in __libc_write_stderr, which makes all host DeathTests pass.
Change-Id: Ic2f6044fdb181eebe132a6f170b57db43c5c3289