If you get this error when trying to start apache, run the following (example uses apache 1.3.37, change the version as needed to match the version you have):
cd /usr/local/directadmin/customapache/apache_1.3.37/src/modules/standard
gcc -shared -o mod_rewrite.so mod_rewrite.lo -lgdbm
cd ../../..
make install
Restart apache and it should be fixed up.
