Update H4 instructions

exercises/h4.md

@@ -350,7 +350,13 @@ apache2-suexec-pristine_2.4.18-2ubuntu3.5_amd64.deb
 apache2-utils_2.4.18-2ubuntu3.5_amd64.deb
 ```
 
-... as a result we can see that the following deb packages should be installed with `dpkg -i` command:
+... as a result you should install the following prerequisites:
+
+```
+sudo apt-get install -y libaprutil1-dbd-sqlite3 libaprutil1-dbd-mysql libaprutil1-dbd-odbc libaprutil1-dbd-pgsql libaprutil1-ldap libmysqlclient20 libodbc1 libpq5 mysql-common
+```
+
+... after which we can install our compiled Apache2 packages with `dpkg -i` command:
 
 ```
 newuser@goauldhost:~/source_codes/apache2$ sudo dpkg -i apache2_2.4.18-2ubuntu3.5_amd64.deb apache2-bin_2.4.18-2ubuntu3.5_amd64.deb apache2-data_2.4.18-2ubuntu3.5_all.deb apache2-utils_2.4.18-2ubuntu3.5_amd64.deb