libc: Make no-debug assert() conform to C requirements
libc: Make no-debug assert() conform to C requirements

The C standard requires assert() to be a void result, so you
could write something like:

  return assert(x), x;

From the C11 standard (7.2 Diagnostic <assert.h>):
> If NDEBUG is defined as a macro name at the point in the source file
> where <assert.h> is included, the assert macro is defined simply as
>    #define assert(ignore) ((void)0)

Signed-off-by: Thiago Macieira <0ed1648d92ca0373297a182b1dba1b974ad10d88@intel.com>

fbsder/zephyr,fbsder/zephyr,GiulianoFranchetto/zephyr,mbolivar/zephyr,kraj/zephyr,ldts/zephyr,zephyriot/zephyr,mbolivar/zephyr,nashif/zephyr,mbolivar/zephyr,zephyrproject-rtos/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,GiulianoFranchetto/zephyr,galak/zephyr,nashif/zephyr,punitvara/zephyr,kraj/zephyr,Vudentz/zephyr,nashif/zephyr,mbolivar/zephyr,aceofall/zephyr-iotos,explora26/zephyr,fbsder/zephyr,explora26/zephyr,zephyrproject-rtos/zephyr,fbsder/zephyr,kraj/zephyr,aceofall/zephyr-iotos,finikorg/zephyr,aceofall/zephyr-iotos,zephyriot/zephyr,ldts/zephyr,Vudentz/zephyr,nashif/zephyr,zephyrproject-rtos/zephyr,ldts/zephyr,ldts/zephyr,zephyriot/zephyr,zephyrproject-rtos/zephyr,aceofall/zephyr-iotos,mbolivar/zephyr,explora26/zephyr,explora26/zephyr,finikorg/zephyr,galak/zephyr,aceofall/zephyr-iotos,GiulianoFranchetto/zephyr,ldts/zephyr,explora26/zephyr,punitvara/zephyr,punitvara/zephyr,zephyriot/zephyr,kraj/zephyr,galak/zephyr,Vudentz/zephyr,zephyriot/zephyr,kraj/zephyr,Vudentz/zephyr,GiulianoFranchetto/zephyr,finikorg/zephyr,finikorg/zephyr,punitvara/zephyr,galak/zephyr,galak/zephyr,nashif/zephyr,fbsder/zephyr,Vudentz/zephyr,Vudentz/zephyr,punitvara/zephyr,zephyrproject-rtos/zephyr