Don't show the "Python 2 interpreter" option in menuconfig when using CMake.
This is a stop-gap until we support Python 2 & 3 together in ESP-IDF (soon).
Closes https://github.com/espressif/esp-idf/issues/1924
Implements support for system level traces compatible with SEGGER
SystemView tool on top of ESP32 application tracing module.
That kind of traces can help to analyse program's behaviour.
SystemView can show timeline of tasks/ISRs execution, context switches,
statistics related to the CPUs' load distribution etc.
Also this commit adds useful feature to ESP32 application tracing module:
- Trace data buffering is implemented to handle temporary peaks of events load
This change adds two options (Debug/Release) for optimization level.
Debug enables -O0, release enables -Os and adds -DNDEBUG (which removes all assert() statements).
Debugging symbols are kept in both cases, although we may add an option to strip output file if necessary.
Also we used to define all common compiler flags in CPPFLAGS, and then appended them to CFLAGS/CXXFLAGS.
It makes it impossible to add preprocessor macros to CPPFLAGS at component level (one has to use CFLAGS/CXXFLAGS instead).
Some third party libraries are not compatible with this approach. Changed to the more common way of using these variables.
