Recently I wanted to be able to sign a package that I was building with The Luggage.

Since The Luggage is calling pkgbuild to build the package, I took a look at the pkgbuild documentation and determined that the following argument was needed :
--sign "Common name of signing cert"

The question then became : how to add this to my Makefile? Taking a look at luggage.make I saw that PB_EXTRA_ARGS is the variable used to contain the arguments for the pkgbuild command.

To add my signing argument, I simply added this line :
PB_EXTRA_ARGS+= --sign "Developer ID Installer: John Doe (ID12345678)"
This appends my –sign argument to the list of pkgbuild arguments and can be placed anywhere after the statement that includes luggage.make.