319.17 installer bug: misdetects MODULE_SIG_FORCE when CC=distcc

I have a low-end htpc where I use distcc by setting CC=“distcc gcc” and CXX=“distcc g++”. The nvidia 319.17 installer then thinks CONFIG_MODULE_SIG_FORCE is set (which it isn’t):

Unable to determine if Secure Boot is enabled: No such file or directory

The target kernel has CONFIG_MODULE_SIG_FORCE set, which means that it requires that kernel modules be cryptographically signed by a trusted key.

Do you already have a key pair which can be used to sign the NVIDIA kernel module? Answer 'Yes' to use an existing key pair, or 'No' to generate a new key pair.

Unsetting CC/CXX, or setting CC=gcc, CXX=g++ fixes the problem.