Enable multiple build output directories

[awvwgk]

This patch implements the possibility to have multiple build output directories depending on the compile flags of the respective target. This will currently only be realized for C objects, since they do not use the compile arguments of any profile.

• remove output_directory from model and replace it with build_prefix the build prefix is generated from the toolchain (Fortran compiler currently)
• output name, directory and file path are saved in target
• object targets can have different module output directories depending on the compile arguments
• all object targets can access all module output directories via include flags (could be refined by providing only access to the required directories from the module interdependencies later)
• all output directories are created in the backend
• executables will include libraries they link against in the build hash
• fix installation of module files

To discuss (possibly for a follow-up patch):

• should executable target include the (all) link arguments in the build hash? Which arguments, only the libs or also the objects?
• should the archive include the object files in the build hash?

To do:

• fix installation of module files

Closes #422

[LKedward]

Thanks Sebastian - I'm quite busy this week, but I should be able to find some time next week to review this.

[awvwgk]

Carlos @brocolis, this should address the issues with relinking the executables upon changes of the link entry in the package manifest now as well.

[LKedward]

Thanks Sebastian - this is a big improvement, nicely implemented.
I know Jakub had to implement something similar for his work - presumably we'll need to merge this into that?

[awvwgk]

I know Jakub had to implement something similar for his work - presumably we'll need to merge this into that?

Exactly, it is based on Jakub's design in #498. I think we can rebase the branch after this change is merged, which should take care of most of the current merge conflicts present.

[kubajj]

I have tried it out and it seems to work as expected. Thank you, Sebastian.

[awvwgk]

Please don't merge yet, I still have to look into collecting all module files from the output directory for fpm install.

[awvwgk]

Will try to finish it this week. Only thing missing is a function that can return the path to all module files from the projects. This should be possible by iterating over the targets and combine the provided module file basenames with the output directory and than copy the complete list in the install command.