create temp directory if it does not exists

[0x53A]

create temp directory if it does not exists

fixes fsprojects/FAKE#1707

[matthid]

I'm not sure if we should just create it. I mean the tmp folder should always exist usually. No idea what you are doing ;). However, I don't mind checking (and therefore improving the error message).
We might consider to throw an IOException just like Path.

[0x53A]

Yeah you are probably right ...

A few versions ago, it did work (I guess fake just didn't access temp at all) , and I got really frustrated after wasting so much time looking for a "stupid" issue, but I guess you are right that the temp folder should always exist ...

Will follow your recommendation and throw an ioexception with an explicit message "temp does not exist".

[matthid]

Maybe even include the path "temp '%s' does not exist" this might make it easier for people to figure out where the invalid path is coming from.