Make configure generate a fake bdb/build_unix/db.h file, so that

'make distcheck' will work.  I hope.

This is an ugly hack....

configure.in

@@ -1906,6 +1906,28 @@ dnl       echo "bdb = '$bdb'; inc = '$bdb_includes', lib = '$bdb_libs'"
     fi
 
     AC_DEFINE(HAVE_BERKELEY_DB)
+  else
+    if test -d bdb; then :
+    else
+      mkdir bdb && mkdir bdb/build_unix && cat <<EOF > bdb/build_unix/db.h
+
+This file is a placeholder to fool make.  The way that automake
+handles 'make distcheck' (calling the VPATH configure with different
+options from the original configure) causes make to think that mysqld
+depends on this file, even though Berkeley DB isn't being used.
+
+Obviously, if this file *is* used, it'll break and hopefully we can find
+out why this file was generated by $(top_srcdir)/configure instead of
+the real db.h.
+
+If you run into some problems because of this file, please use mysql_bug
+to generate a bug report, and give the exact output of make and any
+details you can think of.  Send the message to bugs@lists.mysql.com.
+
+Thank you!
+
+EOF
+    fi
   fi
 
   if test X"$have_innobase_db" = Xyes