Create flags to enable logs when call methods with fibers is in use.

[denihs]

To enable logs using environment variable with params:

ENABLE_LOG_USE_FIBERS=1 to log calls with fibers.
ENABLE_LOG_USE_FIBERS=2 to log calls with fibers and print stack trace.

Usages example:

#!/usr/bin/env bash
echo ">>>>>> NO Log"
node log-fibers-test.js && echo ok
ENABLE_LOG_USE_FIBERS=0 node log-fibers-test.js && echo ok
echo ">>>>>> Log level 1"
ENABLE_LOG_USE_FIBERS=1 node log-fibers-test.js
echo ">>>>>> Log level 2 no filters"
ENABLE_LOG_USE_FIBERS=2 node log-fibers-test.js
echo ">>>>>> Log level 2 with filters matches"
ENABLE_LOG_USE_FIBERS=2 LOG_USE_FIBERS_INCLUDE_IN_PATH=meteor-fibers/node-fibers node log-fibers-test.js
echo ">>>>>> Log level 2 with filters no matches"
ENABLE_LOG_USE_FIBERS=2 LOG_USE_FIBERS_INCLUDE_IN_PATH=meteor-fibers/node2-fibers node log-fibers-test.js

To save all output messages in a file using shell redirect

ENABLE_LOG_USE_FIBERS=2 meteor &> fibers-stack.log