How to specify existing software when building from source?
I'm building sage-7.6 on a CentOS6 machine as per the instructions found on the docs pages, about compiling from source, and it succeeds, but the resulting distribution is 8G in size which is a little unwieldy for deploying to multiple machines.
I notice that it's compiling its own versions of a bunch of things we already have installed, though maybe not at quite exactly the same version number.
Is there a way to use the already installed versions of gcc, python, etc, rather than have sage build its own versions?
It might be possible but not guaranteed to be easy, specially if the versions that you are using do not have features that the sage source uses. Not sure if this will be useful at all, but Arch linux seems to build the sagemath package in this way. You can check out their PGKBUILD file and patches here. PKGBUILD files are more or less easy to follow, but you can read about them here.