Error:  Unable to access jarfile /lib/mxmlc.jar

 I found that this happens when *duh* the mxmlc.jar file cannot be found. Now if we do a vim on the mxmlc file we can see that if we do NOT set the path of the "$FLEX_HOME" var that it will default to wherever mxmlc is located. This should be fine but in some cases wont work if you are calling mxmlc in a odd or different way (i.e. using symlinks or something like that). 

To solve this you can add this into your "mxmlc" file. 

FLEX_HOME='/path/to/flex'

Example. FLEX_HOME='/opt/flex/'

 This should fix any build errors you have when running a flex build via script or using odd/different methods....