RELENG_7_0 buildworld failure on read only source tree

[Tom Judge]

Hi,

We have been building RELENG_6_x source trees from read only NFS file 
systems for well over a year now with out any problems.  However I have 
just tried to do "make buildworld" on a RELENG_7_0 source tree from 
yesterday and it failed to build with the following error:


===> gnu/usr.bin/cvs/cvs (cleandir)
rm -f cvs add.o admin.o annotate.o buffer.o checkin.o checkout.o 
classify.o client.o commit.o create_adm.o cvsrc.o diff.o edit.o 
entries.o error.o expand_path.o fileattr.o filesubr.o find_names.o 
hardlink.o hash.o history.o ignore.o import.o lock.o log.o login.o 
logmsg.o main.o mkmodules.o modules.o myndbm.o no_diff.o parseinfo.o 
patch.o prepend_args.o rcs.o rcscmds.o recurse.o release.o remove.o 
repos.o root.o run.o scramble.o server.o stack.o status.o subr.o tag.o 
update.o vers_ts.o version.o watch.o wrapper.o zlib.o cvs.1.gz cvs.5.gz 
cvs.1.cat.gz cvs.5.cat.gz
rm -rf cvs-sanity
rm -f .depend GPATH GRTAGS GSYMS GTAGS
===> gnu/usr.bin/cvs/contrib (cleandir)
sed -e 's, at CSH@,/bin/csh,' -e 's, at PERL@,/usr/bin/perl,' 
/usr/src/gnu/usr.bin/cvs/contrib/../../../../contrib/cvs/contrib/Makefile.in 
 > Makefile
cannot create Makefile: Read-only file system
*** Error code 2

Stop in /usr/src/gnu/usr.bin/cvs/contrib.
*** Error code 1

Stop in /usr/src/gnu/usr.bin/cvs.
*** Error code 1

Stop in /usr/src/gnu/usr.bin.
*** Error code 1

Stop in /usr/src/gnu.
*** Error code 1

Stop in /usr/src.
*** Error code 1

Stop in /usr/src.
*** Error code 1

Stop in /usr/src.


Should it be possible to build RELENG_7_0 with a read only source tree?

Thanks

Tom