gdbm is only used in tdbspeed and tdbtest which never get
installed, so lets go ahead and force disable gdbm "support"

http://bugs.gentoo.org/113824

--- Makefile.in
+++ Makefile.in
@@ -80,7 +80,7 @@
 @BUILD_TDBTORTURE_TRUE@TDBTORTURE = tdbtorture
 @BUILD_TDBTORTURE_FALSE@TDBTORTURE = 
 
-noinst_PROGRAMS = tdbspeed tdbiterate $(TDBTEST) $(TDBTORTURE)
+noinst_PROGRAMS = tdbiterate $(TDBTORTURE)
 bin_PROGRAMS = tdbtool tdbdump
 
 lib_LTLIBRARIES = libtdb.la