i'm not sure you need to keep doing allclean - i never did when building and got through it ok. it sure will make the whole process veeeeeeery long and painful..
your problem is clearly occurring here:
what os are you running? does it have nptl?
config.status: creating Makefile
config.status: creating db_cxx.h
config.status: creating db_int.h
config.status: creating include.tcl
config.status: creating db.h
config.status: creating db_config.h
make: Entering directory `/tmp/zimbra/ThirdParty/sleepycat/db-126.96.36.199/build_unix'
/bin/sh ./libtool --mode=compile cc -fPIC ../dist/../mutex/mut_pthread.c
cc -fPIC ../dist/../mutex/mut_pthread.c -o mut_pthread.o
../dist/../mutex/mut_pthread.c:8:23: error: db_config.h: No such file or directory
../dist/../mutex/mut_pthread.c:20:20: error: db_int.h: No such file or directory