Posix_GCC: update compiler options
1. Add to CFLAGS
- add -O0 optimization for debug builds.
- add -O3 optimization for release builds.
2. Update signal handler `handle_sigint()` to use
`_exit()` instead of `exit()`. Normal exit() is not allowed
within a signal handler.
Signed-off-by: Florian La Roche <Florian.LaRoche@gmail.com>
This PR enables the FreeRTOS Posix Blinky GCC Demo to be used without the configUSE_TRACE_FACILITY enabled. It is achieved by using `-DNO_TRACING=1` CMake option to disable tracing. By default, -DNO_TRACING is set to 0, and the tracing is enabled.
