Replace the pipe() macro definition with a proper function implementation
to improve POSIX compliance and debugging capabilities. The new pipe()
function serves as a wrapper around pipe2() with flags set to 0.
Changes include:
- Convert pipe() from macro to function declaration in unistd.h
- Add lib_pipe.c implementation file with proper function documentation
- Update build system files (CMakeLists.txt and Make.defs) to include
the new source file when CONFIG_PIPES is enabled
- Add pipe() entry to libc.csv for symbol tracking
This change allows for better debugging, proper symbol resolution,
and follows NuttX coding standards for library function implementations.
Signed-off-by: Huang Qi <huangqi3@xiaomi.com>
311f42bbac