Thanks to simon314's comment as it lead me to the answer.
It seems you can package individual files so I just included all the icon files in the command line like so:
c:\AIRSDK_Compiler\projects\libracalc\src>adt -package -target apk -storetype pk
cs12 -keystore ../cer/JazzCert.p12 ../bin/test.apk test.xml test.swf assets/icon
16.png assets/icon32.png assets/icon48.png assets/icon72.png assets/icon128.png
password:
NOTE: The application has been packaged with a shared runtime.
Success!!