Posix_GCC: update compiler options (#1227)

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>

FreeRTOS/Demo/Posix_GCC/CMakeLists.txt

@@ -4,6 +4,8 @@ project( posix_demo )
 
 add_compile_options( -D_WINDOWS_ )
 
+add_compile_options( -Wall -Wextra -Wpedantic )
+
 if( TRACE_ON_ENTER )
     add_compile_options( -DTRACE_ON_ENTER=1 )
 else()
@@ -33,6 +35,9 @@ else()
     set( CMAKE_BUILD_TYPE "debug" )
 endif()
 
+set(CMAKE_CXX_FLAGS_RELEASE "-O3")
+set(CMAKE_CXX_FLAGS_DEBUG "-O0 -g3")
+
 if( SANITIZE_ADDRESS )
     add_compile_options( -fsanitize=address -fsanitize=alignment )
 endif()

FreeRTOS/Demo/Posix_GCC/main.c

@@ -455,7 +455,7 @@ void handle_sigint( int signal )
         printf( "chdir into %s error is %d\n", BUILD, errno );
     }
 
-    exit( 2 );
+    _exit( 2 );
 }
 
 /*-----------------------------------------------------------*/