Updating SAM/SAMD core breaks ARM compilation on IDE 1.6.6

So… I recently installed IDE 1.6.6 on my Windows 8.1 64 bit machine. Everything was fine until I upgraded the SAM and SAMD cores to the latest versions. After doing this, the IDE has not populated the runtime.tools.arm-none-eabi-gcc.path variable, which prevents it from compiling any SAM or SAMD based boards. The resulting error message looks like so:

exec: “/bin/arm-none-eabi-g++”: file does not exist
Error compiling.

Downgrading the installed cores does not fix the problem, nor does removing and reinstalling IDE 1.6.6. WTF? Has anyone else encountered this problem?

Try renaming your C:\Users{your user name}\AppData\Local\Arduino15 folder and then reinstall Arduino 1.6.6. It should make a new Arduino15 folder the next time you open the IDE. You can copy preferences.txt from the renamed folder to the new Arduino15 folder if you don't want to reset all your preferences. It actually causes the same error message as this issue https://github.com/arduino/Arduino/issues/4130 I reported but that is caused by that file actually being deleted instead of a problem with the the runtime.tools.arm-none-eabi-gcc.path variable.