When rebuilding source, it always have build break on ucb module with error message,

Making:    all_ucpdav.dpslo
Compiling: ucb/wntmsci12.pro/misc/ucpdav1_version.c
Compiling: ucb/source/ucp/webdav/webdavservices.cxx
Compiling: ucb/source/ucp/webdav/webdavprovider.cxx
z:\aoo\r1343539\ucb\source\ucp\webdav\SerfTypes.hxx(27) : fatal error C1083: Can
not open include file: 'serf.h': No such file or directory
dmake:  Error code 2, while making '../../../wntmsci12.pro/slo/webdavprovider.ob
j'

1 module(s):
        ucb
need(s) to be rebuilt

Reason(s):

ERROR: error 65280 occurred while making /cygdrive/z/aoo/r1343539/ucb/source/ucp
/webdav

When you have fixed the errors in that module you can resume the build by runnin
g:

        build --all:ucb

dmake:  Error code 1, while making 'build_instsetoo_native'

The direct error message shows that serf.h is not correctly delivered to solver\340\wntsci12.pro\inc\serf\ at the refresh build time.

The build break can be recreated with 2 scenarios,
  A. After a successful new build. run command "dmake clean" and "dmake". Or
  B. After a successful new build, replace the main directory with a new revision of source code, the problem also appears in the build.


So the problem appears when trying to reuse the previous ext_libraries build result.

The problem can be resolved by manually clear the previous result under ext_libraries directory. So if it can clean the ext_libraries with command "dmake clean", the problem won't appears. This can be easily archived by adding a line to file main/makefile.rc
  	-rm -fr $(foreach,f,$(ADDITIONAL_REPOSITORIES) $f/*/$(INPATH))

But it is still a mystery to me why files serf*.h can not be delivered to solver even if I manually run deliver command under ext_libraries/serf. These original files are not in ext_libraries/serf/wntsci12.pro/inc/ directory.