Bjarni opened the ticket and wrote:

right now when you change Makefile.config, it redo all the dependancies files and all the object files

to prevent needless recompilations, we should store the flags used to compile so we only remake the dependancies files if we changed the source file or we changed the arguments to compile it (we might have changed a flag for linking only)

to make it faster to switch between release and debug builds, the dependancy files and object files should be stored with a prefix of release and debug so we don't overwrite all release object files for making one debug build and then switch back while only changing one source file.

something like .deps/release/(all .o and .d files) would do, but .deps should be renamed if it contains object files as well. It also makes it easier to make clean since you only have to remove one dir

this would also help a lot for building universal binaries if they are stored in .deps/ppc/release and .deps/x86/release. Right now a make clean is needed between each build, so fixing universal binary issues takes a while to compile. This is not needed to be in the first commit of such a feature, it it should be possible to add without redesigning.

Reported version: trunk
Operating system: All

This issue was imported from FlySpray: https://bugs.openttd.org/task/70