psh: ls does not show all the files

[damianloew]

• in this case cp is not visible when running ls on /bin directory, even if ls /bin/cp works properly
• Occurs when building all ports:

TARGET=ia32-generic-qemu LONG_TEST=y CONSOLE=serial ./phoenix-rtos-build/build.sh clean all test

• tested on ia32-generic-qemu (ext2)

• similar behavior:
  

• it seems to be related with psh: some binaries aren't visible when type ls command #194

• probably when more than x files are present in specific directory the issue occurs

[damianloew]

This issue blocks enabling night workflows #294 That's why it's labeled as important