How to capture the compilation options used by Flex Builder

Suppose you are trying to set up a nightly build system – your developers use Flex Builder during the day, and you are creating an Ant task that runs every night. And you want the Ant task to use exactly the same build settings that are used by the developers.

mxmlc and compc have a -dump-config option to dump all settings to a file. Later, the settings in that file can be read back in with -load-config.

So, do this:

• In Flex Builder, do Project Properties
• Click the “Flex Compiler” tab
• In the “Additional compiler arguments” box, add -dump-config «full-path-to-output-file». For example, on Windows, -dump-config C:\myconfig.xml; on Mac, -dump-config /Users/«myname»/myconfig.xml. (If you use a relative path, the file will be put in some odd hard-to-find place.)
• Click OK. If Build Automatically is on, just clicking OK will cause the file to be built; if it is off, do a build now.
• Now that the settings have been dumped, go back to your project settings and remove the -dump-config option.
• Tweak the settings file as necessary (one thing you will almost certainly want to do is change <debug>true</debug> to <debug>false</debug> if your nightly build is supposed to do a release build), and use it in your nightly build script.

Please be aware that this only captures compiler settings; it doesn’t capture all the other little things that Flex Builder does for you, like compiling Flex library projects that your project depends on, copying non-embedded assets to the output directory, optimizing modules for the application, extracting RSLs, copying the HTML template, and so on.

More info here. Please read that, it has additional info you will probably need.