/tmp and /var seperate partitions and noexec

I have recently had some hellish problems trying to get ebuilds to work on my new pentium-classic system running a stage one gentoo install. I think i have discoverd that the problem is that the scripts execute ./configure from the /var or /tmp partiton. Now I was told to mount them "noexec" for security resons. Should this be done only when the system is fully installed and no further modifications are to be made to it? (it is going to be a pure file server so I wont be modifying it a great deal once it is up and running)

That sounds like a plan. Then you can have an upgrade script that sets them exec, updates then resets them to noexec. :D