Buildworld error with read-only source tree

[Justin Hibbits]

On Mon, 7 Nov 2016 20:53:46 -0500
Ryan Stone <rysto32 at gmail.com> wrote:

> I just got the following error attempting to build r308430 with my
> source tree on a read-only NFS mount.  I can work around it for now,
> but shouldn't the source tree be untouched during a buildworld?
> 
> $ make -j4 buildworld buildkernel
> --- buildworld ---
> make[1]: "/repos/users/rstone/freebsd/Makefile.inc1" line 146:
> SYSTEM_COMPILER: Determined that CC=cc matches the source tree.  Not
> bootstrapping a cross-compiler.
> --- buildworld_prologue ---
> --------------------------------------------------------------
> >>> World build started on Tue Nov  8 01:50:50 EST 2016  
> --------------------------------------------------------------
> --- _worldtmp ---
> --------------------------------------------------------------
> >>> Rebuilding the temporary build tree  
> --------------------------------------------------------------
> rm -rf /repos/users/rstone/freebsd/tmp
> rm -rf /repos/users/rstone/freebsd/lib32
> mkdir -p /repos/users/rstone/freebsd/tmp/lib
> mkdir: /repos/users/rstone/freebsd/tmp: Read-only file system

Do you have a MAKEOBJDIRPREFIX set (locally, or through a script or
Makefile hack)? My build log doesn't show it touching the source tree,
it shows it only touching the object tree.

- Justin