From configure scripts to Makefiles?
I'd like to build my own GNU/Linux system from scratch using cross-compilation (just like the CLFS project). Most of the packages I would use are distributed with a configure script, and you just have to run it with the right arguments. For various reasons, I'd like to skip this step, and run make instead. Of course I need a custom Makefile for this to work. The question is: is it feasible to create custom Makefiles without having to read and comprehend all the source code? Is it possible to just read the configure.ac files or something like those? Thanks.
Probably not. What happens is that configure tests which of a number of options are most suited for your environment then substitutes them into Makefile.in to build the Makefile, config.h.in to build config.h etc. You could skip running configure and just determine what these values should be from simple cases of configure.ac (or just keep one huge cache if your environment won't change) but I think packages can define extra inline checks in configure.ac that you'd have to parse and implement correctly. It's going to be a lot easier to just run configure, even if you do have to figure out the correct parameter values for your cross-compiled environment without runtime checks.
However hopefully you only need to build a small number of packages cross (kernel, glibc, gcc, make, bash, etc.), then you can switch into your new environment and build the remaining packages there using configure? If you want inspiration as to what switch values you should be using you can always look at the parameters in Fedora SRPMs or Debian source-debs.