From the adobe documentation
In the Flex Package Explorer, select a project and then right-click (Control-click on Macintosh) to display the context menu and select Properties.
Select the Builders properties page. If you’re using other Eclipse plug-ins, there can be more than one builder listed. Flash Builder provides a builder named Flex, which you cannot modify.
In the Choose Configuration Type dialog box, select the appropriate configuration type. Flash Builder supports the program type. Select it and click OK to continue. From the new builder properties page, you define the builder properties and reference the Ant script (an XML file).
Click OK to apply it to the project
So in the configuration dialog I can also see 'Ant Builder' listed. But in paragraph 4 above it says "Flash Builder supports the program type"
What is the other option Ant Builder for then ? Does that require an install of Ant Builder into Flashbuillder 4.5 whereas Program option is natively supported ? Confused as there is little about the second option 'Ant Builder' in the help files.
Appreciate reply, loosing my hair over this as per usual
I am not the Ant expert that you need and that I want to be.
The configuration of Ant that is included with FB is limited. Extend Eclipse with the Ant (I think it's part of the Java IDE tools).
Then you can create an Ant task that does whatever you want, probably including running the Flex SDK compiler from the command line.
Let me know.