> The interesting thing is that cd'ing into each of the subdirs of /usr/src
> make doing the 'make install'/'make includes' seemed to work (I say seemed,
> because I didn't descend into directories that had already been completed,
> so the total work wasn't as much as a whole-tree 'make install'/'make includes'
> would do).
> 
> Anyone seem anything similar?? Should I file a PR?  Am I just losing my mind?

Yeah, I've had this trying to do exactly the same thing: mount /usr/src on
a convenient machine.  I found that I could cd around and ls and so on,
but when I attempted to do a make build it failed.  

Further investigation showed that it hung when doing actually reading a
file.  Upgrading both machines to a consistent 1.3I allowed me to read
small files, but make build still failed.

1.3K is building on one machine as I write...

David.

PS - Both these machines are arm32.  One has an NE2000 clone and the other
has a dec tulip card (IIRC).