[Buildroot] Buildroot "install" wrapper to preserve file permissions

[Daniel Nyström]

An idea born out of the lately device_table.txt and install issues
discuessed lately.

In other tools similar to Buildroot (e.g. Axis SDK) I've seen an
"install" wrapper which sort of populate an device_table.txt while
installing each component.

In that way, it will preserve any setup, owner and permission on every
file without any global device_table.txt modifications.

(The Axis SDK actually uses meta files in the target dir, but that
would require a whole lot of tool patching while a dynamically written
device_table.txt would work as well)

How would you like this sort of approach in Buildroot?