Fixes for NuttX target

[no1wudi]

Description

Some fixes for NuttX target:

• Add pw_passwd field to struct passwd
• update type of tm_zone/d_name to use c_char type

Sources

src/unix/nuttx/mod.rs

Checklist

• Relevant tests in libc-test/semver have been updated
• No placeholder or unstable values like *LAST or *MAX are
  included (see #3131)
• Tested locally (cd libc-test && cargo test --target mytarget);
  especially relevant for platforms that may not be checked in CI

[rustbot]

r? @tgross35

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[tgross35]

Sources

src/unix/nuttx/mod.rs

For future reference, this is meant to be links to the C source files to cross reference :) but I found these at https://github.com/apache/nuttx/blob/f344a422e8ca8cea6eb31812c1a00fccb7a6d392/include/pwd.h#L49, https://github.com/apache/nuttx/blob/f344a422e8ca8cea6eb31812c1a00fccb7a6d392/include/time.h#L121, https://github.com/apache/nuttx/blob/f344a422e8ca8cea6eb31812c1a00fccb7a6d392/include/dirent.h#L113, looks consistent to me.

@rustbot labeled +stable-nominated