[libposix,libdebug] fix compile issue

[lestLyy]

When I tried to compile on my Ubuntu 22.04, I found that the compilation did not work and there were two compilation issues.

1. Redefine the symbol __start_deflex, I think it was already defined by the linker when creating the segment.
2. Is it a typographical error or is there another reason why popen opened the handle but used fclose.