Can i set a constant for modules dir?

i just noticed upon moving my source dir that many things broke upon the next project re-configuration - such as 'juce' is not a namespace-name and 'String' has not been declared - i eventually tracked this down to being cause by relative paths in the .jucer file

ideally i would like to check this file into source control but these static paths make the .jucer file itself not so portable - is there some way to define a constant for this either in introjucer or perhaps manually splice an environment variable such as $JUCE_MODULES_PATH into the .jucer file - i have yet to try "download and add a module" button - perhaps this is an option ?