Minitrace is a small C++ library used for adding trace points
into the code. When enabled with the build flag
BUILD_LIBRARY_MINITRACE set to true it will write a JSON file
containing these trace points to disk.
This file can be visualized with chromes builtin trace viewer
(about:tracing) which helps in profiling performance issues
and keeping track of performance regression.

Task-number: QDS-3766
Change-Id: I6109a72507b53c5e3ad8f9f504ff26a4fad206be
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Eike Ziller <eike.ziller@qt.io>