[Libreoffice] "modules are inconsistent/missing" during make dev-install

I just noticed that `make dev-install` has been producing
messages ...

|   WARNING(S):
|   Following modules are inconsistent/missing: instsetoo_native
|   Some module(s) contain old output tree(s)!
|   
|   ATTENTION: If you are performing an incompatible build, please break the build with Ctrl+C and 
prepare the workspace with "--prepare" switch!

Should I be concerned?  LibreOffice resulting from previous
builds has run without obvious gross breakage.

I am building on ubuntu-natty with configure options
|   --disable-mozilla
|   --enable-symbols
|   --enable-dbgutil
|   --enable-crashdump
|   --disable-build-mozilla
|   --enable-ext-postgresql-sdbc

FWIW, opengrok finds "inconsisten/missing" only at
solenv/bin/build.pl:2156 in sub prepare_incompatible_build.

Thanks,
Terry.