Reverting Arduino Environment on OS X I am using Arduino environment 1.6.17 on OS X, 10.12.2. In this version, all of the core avr library stuff is located in ~/Library/Arduino15. 

I was told by a vendor that in order for their program to compile properly, I needed to compile it under 1.6.4 of the Arduino environment. I dowloaded that version and compiled the program again. I could tell though, by the compiler messages, that while the IDE may be version 1.6.4, the program was still compiling with version 1.6.17 tools and avr libraries. Is there anyway to change that so I can get it to actually compile with all tools and libs from 1.6.4?
I didn't try the total removal of the environment and then a re-installation as JRobert suggested, because I didn't really want to nuke my current environment. But his post did inspire me to try and run the 1.6.4 environment from another user account that had never run any Arduino stuff before. This seemed functionally equivalent to his or her suggestion. That seemed to work. Although, I still have a feeling that there is a more convenient solution out there.