liblog: add LOGGER_STDERR frontend
Standalone, this logger provides no end-to-end capability. Only
provides a writer, no reader transport. All output goes, logcat-like,
into the stderr stream. Output can be adjusted with environment
variables ANDROID_PRINTF_LOG and ANDROID_LOG_TAGS.
liblog_*.__android_log_bswrite_and_print___max print fails if a string
member is truncated with "Binary log entry conversion failed" and -1.
We expose the truncated content in the tests and in LOGGER_STDERR.
The purpose of this transport selection is for command-line tools,
providing a means to shunt the logs to be mixed in with the tool's
error stream.
Test: gTest liblog-unit-tests
Bug: 27405083
Change-Id: If344b6e3e67df2dc86ce317cfad8af8e857727b7
9 files changed