Support make variable substitution in prefix

[criemen]

Hi,

you're supporting make variable substitution in package_file_name, and custom variables can be supplied via toolchains. That's great!
I'm using this to create platform-specific file names.
However, in our software, we're also packaging platform-specific files into folders with a platform-specific name.
For that, we currently use prefix (of pkg_filegroup) in combination with select.
Unfortunately, prefix doesn't support make variable substitution, and therefore we need to have two mechanisms for the same thing.
Would it be possible to enable make variable substitution for prefix as well?
I've not checked other places, but I assume make variable substitution could also come in handy for renames, and other places where generic file paths are specified.

[aiuto]

It would certainly be possible. It's just a matter of finding time to add it.

[aiuto]

Well.... 2.5 years later, I definitely need this in my current job.
So, I'm going to try it.