Change php modules directory
I would suggest making /usr/lib64/php/modules a symlink to the folder with the ID. This prevents mixing extensions from different versions of PHP in the long run.
Besides that: You should be able to set it by setting EXTENSION_DIR as environment variable before running PHP's configure. something like
$ EXTENSION_DIR=/my/location ./configure --with-some-extension
Check the current extension directory with:
php-config --extension-dir
and you can change it by setting extension_dir in php.ini:
extension_dir="/usr/lib64/php/modules"
Don't forget to restart Apache.