We have project which uses gcc and make files. Project also contains of one big subproject (SDK) and a lot of relatively small subprojects which use that SDK and some shared framework.
We use precompiled headers, but that helps only for re-compilation to be faster.
Is there any known techniques and tools to help with build-time optimizations? Or maybe you know some articles/resources about this or related topics?
You can tackle the problem from two sides: refactor the code to reduce the complexity the compiler is seeing, or speed up the compiler execution.
Without touching the code, you can add more compilation power into it. Use ccache to avoid recompiling files you have already compiled and distcc to distribute the build time among more machines. Use make -j where N is the number of cores+1 if you compile locally, or a bigger number for distributed builds. That flag will run more than one compiler in parallel.
Refactoring the code. Prefer forward declaration to includes (simple). Decouple as much as you can to avoid dependencies (use the PIMPL idiom).
Template instantiation is expensive, they are recompiled in every compilation unit that uses them. If you can refactor your templates as to forward declare them and then instantiate them in only one compilation unit.