It is very rare that you will need to compile Alfresco from source. The source is definitely handy to have, because it often assists with troubleshooting or with understanding how the product is built and extended, but for most projects, compiling from source is unnecessary.
Instead, if you are looking to make configuration changes or extend the platform you should start with the Maven-based Alfresco SDK. Using the Alfresco SDK you'll be able to launch and run Alfresco on your machine and you'll be able to make and test config changes and customizations. The SDK will also produce artifacts that you can deploy into your Alfresco server installation.