MAKE EXPORT LIMITATIONS

```
Description: The top-level Makefile 'export' target that will bundle up all of the
NuttX libraries, header files, and the startup object into an export-able
tarball. This target uses the tools/mkexport.sh script. Issues:

1. This script assumes the host archiver ar may not be appropriate for
non-GCC toolchains
2. For the kernel build, the user libraries should be built into some
libuser.a. The list of user libraries would have to accepted with
some new argument, perhaps -u.
Status: Open
Priority: Low.
```

Start with the top-level Makefile's export target and tools/mkexport.sh. Trace how the script archives NuttX libraries, headers, and the startup object, then inspect how host ar and kernel user libraries are selected. Done means the export handles non-GCC archivers and accepts the user-library list for a libuser.a.

Written by the indexing model from the issue text.